six.py

"""
Utilities for writing code that runs on Python 2 and 3

According to https://pypi.org/project/six/:

Six is a Python 2 and 3 compatibility library. It provides utility functions
for smoothing over the differences between the Python versions with the goal of
writing Python code that is compatible on both Python versions.
"""

from __future__ import absolute_import

import functools
import operator
import sys
import types

__author__ = "Benjamin Peterson <benjamin@python.org>"
__version__ = "1.8.0"


# Useful for very coarse version differentiation.
PY2 = sys.version_info[0] == 2
PY3 = sys.version_info[0] == 3

if PY3:
    string_types = str,
    integer_types = int,
    class_types = type,
    text_type = str
    binary_type = bytes

    MAXSIZE = sys.maxsize
else:
    string_types = basestring,
    integer_types = (int, long)
    class_types = (type, types.ClassType)
    text_type = unicode
    binary_type = str

    if sys.platform.startswith("java"):
        # Jython always uses 32 bits.
        MAXSIZE = int((1 << 31) - 1)
    else:
        # It's possible to have sizeof(long) != sizeof(Py_ssize_t).
        class X(object):
            def __len__(self):
                return 1 << 31
        try:
            len(X())
        except OverflowError:
            # 32-bit
            MAXSIZE = int((1 << 31) - 1)
        else:
            # 64-bit
            MAXSIZE = int((1 << 63) - 1)
        del X


def _add_doc(func, doc):
    """Add documentation to a function."""
    func.__doc__ = doc


def _import_module(name):
    """Import module, returning the module after the last dot."""
    __import__(name)
    return sys.modules[name]


class _LazyDescr(object):

    def __init__(self, name):
        self.name = name

    def __get__(self, obj, tp):
        result = self._resolve()
        setattr(obj, self.name, result) # Invokes __set__.
        # This is a bit ugly, but it avoids running this again.
        delattr(obj.__class__, self.name)
        return result


class MovedModule(_LazyDescr):

    def __init__(self, name, old, new=None):
        super(MovedModule, self).__init__(name)
        if PY3:
            if new is None:
                new = name
            self.mod = new
        else:
            self.mod = old

    def _resolve(self):
        return _import_module(self.mod)

    def __getattr__(self, attr):
        _module = self._resolve()
        value = getattr(_module, attr)
        setattr(self, attr, value)
        return value


class _LazyModule(types.ModuleType):

    def __init__(self, name):
        super(_LazyModule, self).__init__(name)
        self.__doc__ = self.__class__.__doc__

    def __dir__(self):
        attrs = ["__doc__", "__name__"]
        attrs += [attr.name for attr in self._moved_attributes]
        return attrs

    # Subclasses should override this
    _moved_attributes = []


class MovedAttribute(_LazyDescr):

    def __init__(self, name, old_mod, new_mod, old_attr=None, new_attr=None):
        super(MovedAttribute, self).__init__(name)
        if PY3:
            if new_mod is None:
                new_mod = name
            self.mod = new_mod
            if new_attr is None:
                if old_attr is None:
                    new_attr = name
                else:
                    new_attr = old_attr
            self.attr = new_attr
        else:
            self.mod = old_mod
            if old_attr is None:
                old_attr = name
            self.attr = old_attr

    def _resolve(self):
        module = _import_module(self.mod)
        return getattr(module, self.attr)


class _SixMetaPathImporter(object):
    """
    A meta path importer to import six.moves and its submodules.

    This class implements a PEP302 finder and loader. It should be compatible
    with Python 2.5 and all existing versions of Python3
    """
    def __init__(self, six_module_name):
        self.name = six_module_name
        self.known_modules = {}

    def _add_module(self, mod, *fullnames):
        for fullname in fullnames:
            self.known_modules[self.name + "." + fullname] = mod

    def _get_module(self, fullname):
        return self.known_modules[self.name + "." + fullname]

    def find_module(self, fullname, path=None):
        if fullname in self.known_modules:
            return self
        return None

    def __get_module(self, fullname):
        try:
            return self.known_modules[fullname]
        except KeyError:
            raise ImportError("This loader does not know module " + fullname)

    def load_module(self, fullname):
        try:
            # in case of a reload
            return sys.modules[fullname]
        except KeyError:
            pass
        mod = self.__get_module(fullname)
        if isinstance(mod, MovedModule):
            mod = mod._resolve()
        else:
            mod.__loader__ = self
        sys.modules[fullname] = mod
        return mod

    def is_package(self, fullname):
        """
        Return true, if the named module is a package.

        We need this method to get correct spec objects with
        Python 3.4 (see PEP451)
        """
        return hasattr(self.__get_module(fullname), "__path__")

    def get_code(self, fullname):
        """Return None

        Required, if is_package is implemented"""
        self.__get_module(fullname)  # eventually raises ImportError
        return None
    get_source = get_code  # same as get_code

_importer = _SixMetaPathImporter(__name__)


class _MovedItems(_LazyModule):
    """Lazy loading of moved objects"""
    __path__ = []  # mark as package


_moved_attributes = [
    MovedAttribute("cStringIO", "cStringIO", "io", "StringIO"),
    MovedAttribute("filter", "itertools", "builtins", "ifilter", "filter"),
    MovedAttribute("filterfalse", "itertools", "itertools", "ifilterfalse", "filterfalse"),
    MovedAttribute("input", "__builtin__", "builtins", "raw_input", "input"),
    MovedAttribute("intern", "__builtin__", "sys"),
    MovedAttribute("map", "itertools", "builtins", "imap", "map"),
    MovedAttribute("range", "__builtin__", "builtins", "xrange", "range"),
    MovedAttribute("reload_module", "__builtin__", "imp", "reload"),
    MovedAttribute("reduce", "__builtin__", "functools"),
    MovedAttribute("shlex_quote", "pipes", "shlex", "quote"),
    MovedAttribute("StringIO", "StringIO", "io"),
    MovedAttribute("UserDict", "UserDict", "collections"),
    MovedAttribute("UserList", "UserList", "collections"),
    MovedAttribute("UserString", "UserString", "collections"),
    MovedAttribute("xrange", "__builtin__", "builtins", "xrange", "range"),
    MovedAttribute("zip", "itertools", "builtins", "izip", "zip"),
    MovedAttribute("zip_longest", "itertools", "itertools", "izip_longest", "zip_longest"),

    MovedModule("builtins", "__builtin__"),
    MovedModule("configparser", "ConfigParser"),
    MovedModule("copyreg", "copy_reg"),
    MovedModule("dbm_gnu", "gdbm", "dbm.gnu"),
    MovedModule("_dummy_thread", "dummy_thread", "_dummy_thread"),
    MovedModule("http_cookiejar", "cookielib", "http.cookiejar"),
    MovedModule("http_cookies", "Cookie", "http.cookies"),
    MovedModule("html_entities", "htmlentitydefs", "html.entities"),
    MovedModule("html_parser", "HTMLParser", "html.parser"),
    MovedModule("http_client", "httplib", "http.client"),
    MovedModule("email_mime_multipart", "email.MIMEMultipart", "email.mime.multipart"),
    MovedModule("email_mime_nonmultipart", "email.MIMENonMultipart", "email.mime.nonmultipart"),
    MovedModule("email_mime_text", "email.MIMEText", "email.mime.text"),
    MovedModule("email_mime_base", "email.MIMEBase", "email.mime.base"),
    MovedModule("BaseHTTPServer", "BaseHTTPServer", "http.server"),
    MovedModule("CGIHTTPServer", "CGIHTTPServer", "http.server"),
    MovedModule("SimpleHTTPServer", "SimpleHTTPServer", "http.server"),
    MovedModule("cPickle", "cPickle", "pickle"),
    MovedModule("queue", "Queue"),
    MovedModule("reprlib", "repr"),
    MovedModule("socketserver", "SocketServer"),
    MovedModule("_thread", "thread", "_thread"),
    MovedModule("tkinter", "Tkinter"),
    MovedModule("tkinter_dialog", "Dialog", "tkinter.dialog"),
    MovedModule("tkinter_filedialog", "FileDialog", "tkinter.filedialog"),
    MovedModule("tkinter_scrolledtext", "ScrolledText", "tkinter.scrolledtext"),
    MovedModule("tkinter_simpledialog", "SimpleDialog", "tkinter.simpledialog"),
    MovedModule("tkinter_tix", "Tix", "tkinter.tix"),
    MovedModule("tkinter_ttk", "ttk", "tkinter.ttk"),
    MovedModule("tkinter_constants", "Tkconstants", "tkinter.constants"),
    MovedModule("tkinter_dnd", "Tkdnd", "tkinter.dnd"),
    MovedModule("tkinter_colorchooser", "tkColorChooser",
                "tkinter.colorchooser"),
    MovedModule("tkinter_commondialog", "tkCommonDialog",
                "tkinter.commondialog"),
    MovedModule("tkinter_tkfiledialog", "tkFileDialog", "tkinter.filedialog"),
    MovedModule("tkinter_font", "tkFont", "tkinter.font"),
    MovedModule("tkinter_messagebox", "tkMessageBox", "tkinter.messagebox"),
    MovedModule("tkinter_tksimpledialog", "tkSimpleDialog",
                "tkinter.simpledialog"),
    MovedModule("urllib_parse", __name__ + ".moves.urllib_parse", "urllib.parse"),
    MovedModule("urllib_error", __name__ + ".moves.urllib_error", "urllib.error"),
    MovedModule("urllib", __name__ + ".moves.urllib", __name__ + ".moves.urllib"),
    MovedModule("urllib_robotparser", "robotparser", "urllib.robotparser"),
    MovedModule("xmlrpc_client", "xmlrpclib", "xmlrpc.client"),
    MovedModule("xmlrpc_server", "SimpleXMLRPCServer", "xmlrpc.server"),
    MovedModule("winreg", "_winreg"),
]
for attr in _moved_attributes:
    setattr(_MovedItems, attr.name, attr)
    if isinstance(attr, MovedModule):
        _importer._add_module(attr, "moves." + attr.name)
del attr

_MovedItems._moved_attributes = _moved_attributes

moves = _MovedItems(__name__ + ".moves")
_importer._add_module(moves, "moves")


class Module_six_moves_urllib_parse(_LazyModule):
    """Lazy loading of moved objects in six.moves.urllib_parse"""


_urllib_parse_moved_attributes = [
    MovedAttribute("ParseResult", "urlparse", "urllib.parse"),
    MovedAttribute("SplitResult", "urlparse", "urllib.parse"),
    MovedAttribute("parse_qs", "urlparse", "urllib.parse"),
    MovedAttribute("parse_qsl", "urlparse", "urllib.parse"),
    MovedAttribute("urldefrag", "urlparse", "urllib.parse"),
    MovedAttribute("urljoin", "urlparse", "urllib.parse"),
    MovedAttribute("urlparse", "urlparse", "urllib.parse"),
    MovedAttribute("urlsplit", "urlparse", "urllib.parse"),
    MovedAttribute("urlunparse", "urlparse", "urllib.parse"),
    MovedAttribute("urlunsplit", "urlparse", "urllib.parse"),
    MovedAttribute("quote", "urllib", "urllib.parse"),
    MovedAttribute("quote_plus", "urllib", "urllib.parse"),
    MovedAttribute("unquote", "urllib", "urllib.parse"),
    MovedAttribute("unquote_plus", "urllib", "urllib.parse"),
    MovedAttribute("urlencode", "urllib", "urllib.parse"),
    MovedAttribute("splitquery", "urllib", "urllib.parse"),
    MovedAttribute("splittag", "urllib", "urllib.parse"),
    MovedAttribute("splituser", "urllib", "urllib.parse"),
    MovedAttribute("uses_fragment", "urlparse", "urllib.parse"),
    MovedAttribute("uses_netloc", "urlparse", "urllib.parse"),
    MovedAttribute("uses_params", "urlparse", "urllib.parse"),
    MovedAttribute("uses_query", "urlparse", "urllib.parse"),
    MovedAttribute("uses_relative", "urlparse", "urllib.parse"),
]
for attr in _urllib_parse_moved_attributes:
    setattr(Module_six_moves_urllib_parse, attr.name, attr)
del attr

Module_six_moves_urllib_parse._moved_attributes = _urllib_parse_moved_attributes

_importer._add_module(Module_six_moves_urllib_parse(__name__ + ".moves.urllib_parse"),
                      "moves.urllib_parse", "moves.urllib.parse")


class Module_six_moves_urllib_error(_LazyModule):
    """Lazy loading of moved objects in six.moves.urllib_error"""


_urllib_error_moved_attributes = [
    MovedAttribute("URLError", "urllib2", "urllib.error"),
    MovedAttribute("HTTPError", "urllib2", "urllib.error"),
    MovedAttribute("ContentTooShortError", "urllib", "urllib.error"),
]
for attr in _urllib_error_moved_attributes:
    setattr(Module_six_moves_urllib_error, attr.name, attr)
del attr

Module_six_moves_urllib_error._moved_attributes = _urllib_error_moved_attributes

_importer._add_module(Module_six_moves_urllib_error(__name__ + ".moves.urllib.error"),
                      "moves.urllib_error", "moves.urllib.error")


class Module_six_moves_urllib_request(_LazyModule):
    """Lazy loading of moved objects in six.moves.urllib_request"""


_urllib_request_moved_attributes = [
    MovedAttribute("urlopen", "urllib2", "urllib.request"),
    MovedAttribute("install_opener", "urllib2", "urllib.request"),
    MovedAttribute("build_opener", "urllib2", "urllib.request"),
    MovedAttribute("pathname2url", "urllib", "urllib.request"),
    MovedAttribute("url2pathname", "urllib", "urllib.request"),
    MovedAttribute("getproxies", "urllib", "urllib.request"),
    MovedAttribute("Request", "urllib2", "urllib.request"),
    MovedAttribute("OpenerDirector", "urllib2", "urllib.request"),
    MovedAttribute("HTTPDefaultErrorHandler", "urllib2", "urllib.request"),
    MovedAttribute("HTTPRedirectHandler", "urllib2", "urllib.request"),
    MovedAttribute("HTTPCookieProcessor", "urllib2", "urllib.request"),
    MovedAttribute("ProxyHandler", "urllib2", "urllib.request"),
    MovedAttribute("BaseHandler", "urllib2", "urllib.request"),
    MovedAttribute("HTTPPasswordMgr", "urllib2", "urllib.request"),
    MovedAttribute("HTTPPasswordMgrWithDefaultRealm", "urllib2", "urllib.request"),
    MovedAttribute("AbstractBasicAuthHandler", "urllib2", "urllib.request"),
    MovedAttribute("HTTPBasicAuthHandler", "urllib2", "urllib.request"),
    MovedAttribute("ProxyBasicAuthHandler", "urllib2", "urllib.request"),
    MovedAttribute("AbstractDigestAuthHandler", "urllib2", "urllib.request"),
    MovedAttribute("HTTPDigestAuthHandler", "urllib2", "urllib.request"),
    MovedAttribute("ProxyDigestAuthHandler", "urllib2", "urllib.request"),
    MovedAttribute("HTTPHandler", "urllib2", "urllib.request"),
    MovedAttribute("HTTPSHandler", "urllib2", "urllib.request"),
    MovedAttribute("FileHandler", "urllib2", "urllib.request"),
    MovedAttribute("FTPHandler", "urllib2", "urllib.request"),
    MovedAttribute("CacheFTPHandler", "urllib2", "urllib.request"),
    MovedAttribute("UnknownHandler", "urllib2", "urllib.request"),
    MovedAttribute("HTTPErrorProcessor", "urllib2", "urllib.request"),
    MovedAttribute("urlretrieve", "urllib", "urllib.request"),
    MovedAttribute("urlcleanup", "urllib", "urllib.request"),
    MovedAttribute("URLopener", "urllib", "urllib.request"),
    MovedAttribute("FancyURLopener", "urllib", "urllib.request"),
    MovedAttribute("proxy_bypass", "urllib", "urllib.request"),
]
for attr in _urllib_request_moved_attributes:
    setattr(Module_six_moves_urllib_request, attr.name, attr)
del attr

Module_six_moves_urllib_request._moved_attributes = _urllib_request_moved_attributes

_importer._add_module(Module_six_moves_urllib_request(__name__ + ".moves.urllib.request"),
                      "moves.urllib_request", "moves.urllib.request")


class Module_six_moves_urllib_response(_LazyModule):
    """Lazy loading of moved objects in six.moves.urllib_response"""


_urllib_response_moved_attributes = [
    MovedAttribute("addbase", "urllib", "urllib.response"),
    MovedAttribute("addclosehook", "urllib", "urllib.response"),
    MovedAttribute("addinfo", "urllib", "urllib.response"),
    MovedAttribute("addinfourl", "urllib", "urllib.response"),
]
for attr in _urllib_response_moved_attributes:
    setattr(Module_six_moves_urllib_response, attr.name, attr)
del attr

Module_six_moves_urllib_response._moved_attributes = _urllib_response_moved_attributes

_importer._add_module(Module_six_moves_urllib_response(__name__ + ".moves.urllib.response"),
                      "moves.urllib_response", "moves.urllib.response")


class Module_six_moves_urllib_robotparser(_LazyModule):
    """Lazy loading of moved objects in six.moves.urllib_robotparser"""


_urllib_robotparser_moved_attributes = [
    MovedAttribute("RobotFileParser", "robotparser", "urllib.robotparser"),
]
for attr in _urllib_robotparser_moved_attributes:
    setattr(Module_six_moves_urllib_robotparser, attr.name, attr)
del attr

Module_six_moves_urllib_robotparser._moved_attributes = _urllib_robotparser_moved_attributes

_importer._add_module(Module_six_moves_urllib_robotparser(__name__ + ".moves.urllib.robotparser"),
                      "moves.urllib_robotparser", "moves.urllib.robotparser")


class Module_six_moves_urllib(types.ModuleType):
    """Create a six.moves.urllib namespace that resembles the Python 3 namespace"""
    __path__ = []  # mark as package
    parse = _importer._get_module("moves.urllib_parse")
    error = _importer._get_module("moves.urllib_error")
    request = _importer._get_module("moves.urllib_request")
    response = _importer._get_module("moves.urllib_response")
    robotparser = _importer._get_module("moves.urllib_robotparser")

    def __dir__(self):
        return ['parse', 'error', 'request', 'response', 'robotparser']

_importer._add_module(Module_six_moves_urllib(__name__ + ".moves.urllib"),
                      "moves.urllib")


def add_move(move):
    """Add an item to six.moves."""
    setattr(_MovedItems, move.name, move)


def remove_move(name):
    """Remove item from six.moves."""
    try:
        delattr(_MovedItems, name)
    except AttributeError:
        try:
            del moves.__dict__[name]
        except KeyError:
            raise AttributeError("no such move, %r" % (name,))


if PY3:
    _meth_func = "__func__"
    _meth_self = "__self__"

    _func_closure = "__closure__"
    _func_code = "__code__"
    _func_defaults = "__defaults__"
    _func_globals = "__globals__"
else:
    _meth_func = "im_func"
    _meth_self = "im_self"

    _func_closure = "func_closure"
    _func_code = "func_code"
    _func_defaults = "func_defaults"
    _func_globals = "func_globals"


try:
    advance_iterator = next
except NameError:
    def advance_iterator(it):
        return it.next()
next = advance_iterator


try:
    callable = callable
except NameError:
    def callable(obj):
        return any("__call__" in klass.__dict__ for klass in type(obj).__mro__)


if PY3:
    def get_unbound_function(unbound):
        return unbound

    create_bound_method = types.MethodType

    Iterator = object
else:
    def get_unbound_function(unbound):
        return unbound.im_func

    def create_bound_method(func, obj):
        return types.MethodType(func, obj, obj.__class__)

    class Iterator(object):

        def next(self):
            return type(self).__next__(self)

    callable = callable
_add_doc(get_unbound_function,
         """Get the function out of a possibly unbound function""")


get_method_function = operator.attrgetter(_meth_func)
get_method_self = operator.attrgetter(_meth_self)
get_function_closure = operator.attrgetter(_func_closure)
get_function_code = operator.attrgetter(_func_code)
get_function_defaults = operator.attrgetter(_func_defaults)
get_function_globals = operator.attrgetter(_func_globals)


if PY3:
    def iterkeys(d, **kw):
        return iter(d.keys(**kw))

    def itervalues(d, **kw):
        return iter(d.values(**kw))

    def iteritems(d, **kw):
        return iter(d.items(**kw))

    def iterlists(d, **kw):
        return iter(d.lists(**kw))
else:
    def iterkeys(d, **kw):
        return iter(d.iterkeys(**kw))

    def itervalues(d, **kw):
        return iter(d.itervalues(**kw))

    def iteritems(d, **kw):
        return iter(d.iteritems(**kw))

    def iterlists(d, **kw):
        return iter(d.iterlists(**kw))

_add_doc(iterkeys, "Return an iterator over the keys of a dictionary.")
_add_doc(itervalues, "Return an iterator over the values of a dictionary.")
_add_doc(iteritems,
         "Return an iterator over the (key, value) pairs of a dictionary.")
_add_doc(iterlists,
         "Return an iterator over the (key, [values]) pairs of a dictionary.")


if PY3:
    def b(s):
        return s.encode("latin-1")
    def u(s):
        return s
    unichr = chr
    if sys.version_info[1] <= 1:
        def int2byte(i):
            return bytes((i,))
    else:
        # This is about 2x faster than the implementation above on 3.2+
        int2byte = operator.methodcaller("to_bytes", 1, "big")
    byte2int = operator.itemgetter(0)
    indexbytes = operator.getitem
    iterbytes = iter
    import io
    StringIO = io.StringIO
    BytesIO = io.BytesIO
else:
    def b(s):
        return s
    # Workaround for standalone backslash
    def u(s):
        return unicode(s.replace(r'\\', r'\\\\'), "unicode_escape")
    unichr = unichr
    int2byte = chr
    def byte2int(bs):
        return ord(bs[0])
    def indexbytes(buf, i):
        return ord(buf[i])
    def iterbytes(buf):
        return (ord(byte) for byte in buf)
    import StringIO
    StringIO = BytesIO = StringIO.StringIO
_add_doc(b, """Byte literal""")
_add_doc(u, """Text literal""")


if PY3:
    exec_ = getattr(moves.builtins, "exec")


    def reraise(tp, value, tb=None):
        if value is None:
            value = tp()
        if value.__traceback__ is not tb:
            raise value.with_traceback(tb)
        raise value

else:
    def exec_(_code_, _globs_=None, _locs_=None):
        """Execute code in a namespace."""
        if _globs_ is None:
            frame = sys._getframe(1)
            _globs_ = frame.f_globals
            if _locs_ is None:
                _locs_ = frame.f_locals
            del frame
        elif _locs_ is None:
            _locs_ = _globs_
        exec("""exec _code_ in _globs_, _locs_""")


    exec_("""def reraise(tp, value, tb=None):
    raise tp, value, tb
""")


print_ = getattr(moves.builtins, "print", None)
if print_ is None:
    def print_(*args, **kwargs):
        """The new-style print function for Python 2.4 and 2.5."""
        fp = kwargs.pop("file", sys.stdout)
        if fp is None:
            return
        def write(data):
            if not isinstance(data, basestring):
                data = str(data)
            # If the file has an encoding, encode unicode with it.
            if (isinstance(fp, file) and
                isinstance(data, unicode) and
                fp.encoding is not None):
                errors = getattr(fp, "errors", None)
                if errors is None:
                    errors = "strict"
                data = data.encode(fp.encoding, errors)
            fp.write(data)
        want_unicode = False
        sep = kwargs.pop("sep", None)
        if sep is not None:
            if isinstance(sep, unicode):
                want_unicode = True
            elif not isinstance(sep, str):
                raise TypeError("sep must be None or a string")
        end = kwargs.pop("end", None)
        if end is not None:
            if isinstance(end, unicode):
                want_unicode = True
            elif not isinstance(end, str):
                raise TypeError("end must be None or a string")
        if kwargs:
            raise TypeError("invalid keyword arguments to print()")
        if not want_unicode:
            for arg in args:
                if isinstance(arg, unicode):
                    want_unicode = True
                    break
        if want_unicode:
            newline = unicode("\n")
            space = unicode(" ")
        else:
            newline = "\n"
            space = " "
        if sep is None:
            sep = space
        if end is None:
            end = newline
        for i, arg in enumerate(args):
            if i:
                write(sep)
            write(arg)
        write(end)

_add_doc(reraise, """Reraise an exception.""")

if sys.version_info[0:2] < (3, 4):
    def wraps(wrapped, assigned=functools.WRAPPER_ASSIGNMENTS,
              updated=functools.WRAPPER_UPDATES):
        def wrapper(f):
            f = functools.wraps(wrapped)(f)
            f.__wrapped__ = wrapped
            return f
        return wrapper
else:
    wraps = functools.wraps

def with_metaclass(meta, *bases):
    """Create a base class with a metaclass."""
    # This requires a bit of explanation: the basic idea is to make a dummy
    # metaclass for one level of class instantiation that replaces itself with
    # the actual metaclass.
    class metaclass(meta):
        def __new__(cls, name, this_bases, d):
            return meta(name, bases, d)
    return type.__new__(metaclass, 'temporary_class', (), {})


def add_metaclass(metaclass):
    """Class decorator for creating a class with a metaclass."""
    def wrapper(cls):
        orig_vars = cls.__dict__.copy()
        slots = orig_vars.get('__slots__')
        if slots is not None:
            if isinstance(slots, str):
                slots = [slots]
            for slots_var in slots:
                orig_vars.pop(slots_var)
        orig_vars.pop('__dict__', None)
        orig_vars.pop('__weakref__', None)
        return metaclass(cls.__name__, cls.__bases__, orig_vars)
    return wrapper

# Complete the moves implementation.
# This code is at the end of this module to speed up module loading.
# Turn this module into a package.
__path__ = []  # required for PEP 302 and PEP 451
__package__ = __name__  # see PEP 366 @ReservedAssignment
if globals().get("__spec__") is not None:
    __spec__.submodule_search_locations = []  # PEP 451 @UndefinedVariable
# Remove other six meta path importers, since they cause problems. This can
# happen if six is removed from sys.modules and then reloaded. (Setuptools does
# this for some reason.)
if sys.meta_path:
    for i, importer in enumerate(sys.meta_path):
        # Here's some real nastiness: Another "instance" of the six module might
        # be floating around. Therefore, we can't use isinstance() to check for
        # the six meta path importer, since the other six instance will have
        # inserted an importer with different class.
        if (type(importer).__name__ == "_SixMetaPathImporter" and
            importer.name == __name__):
            del sys.meta_path[i]
            break
    del i, importer
# Finally, add the importer to the meta path import hook.
sys.meta_path.append(_importer)