Sphinx: Fix Errors/Warnings

Fix a few Sphinx errors/warnings that I saw when building locally.

docs/source/usage/python.rst

@@ -780,7 +780,7 @@ This module provides elements for the accelerator lattice.
    :param ds: Segment length in m.
    :param k:  focusing strength in m^(-2) (if unit = 0)
               = (azimuthal magnetic field gradient in T/m) / (rigidity in T-m)
-          OR  azimuthal magnetic field gradient in T/m (if unit = 1)
+              OR  azimuthal magnetic field gradient in T/m (if unit = 1)
    :param unit: specification of units for plasma lens focusing strength
    :param dx: horizontal translation error in m
    :param dy: vertical translation error in m
@@ -901,7 +901,7 @@ This module provides elements for the accelerator lattice.
    :param ds: Segment length in m.
    :param bscale: Scaling factor for on-axis magnetic field Bz in inverse meters (if unit = 0)
               = (magnetic field Bz in T) / (rigidity in T-m)
-          OR  Magnetic field Bz in T (SI units, if unit = 1)
+              OR  Magnetic field Bz in T (SI units, if unit = 1)
    :param cos_coefficients: array of ``float`` cosine coefficients in Fourier expansion of on-axis magnetic field Bz
             (optional); default is a thin-shell model from `DOI:10.1016/J.NIMA.2022.166706 <https://doi.org/10.1016/j.nima.2022.166706>`__
    :param sin_coefficients: array of ``float`` sine coefficients in Fourier expansion of on-axis magnetic field Bz

examples/cfchannel/README.rst

@@ -81,28 +81,42 @@ The initial distribution used is a 6D waterbag.
 The beam second moments should remain nearly unchanged, except for some small emittance growth due to nonlinear space charge.
 This is tested using the second moments of the distribution.
 
-In this test, the initial and final values of :math:`\sigma_x`, :math:`\sigma_y`, :math:`\sigma_t`, :math:`\epsilon_x`, :math:`\epsilon_y`, and :math:`
+In this test, the initial and final values of :math:`\sigma_x`, :math:`\sigma_y`, :math:`\sigma_t`, :math:`\epsilon_x`, :math:`\epsilon_y`, and :math:`\epsilon_t` must agree with nominal values.
 
 
 Run
 ---
 
-This example can be run as a Python script (``python3 run_cfchannel_10nC.py``) or  as an app with an input file (``impactx input_cfchannel_10nC.in``).
+This example can be run as a Python script (``python3 run_cfchannel_10nC_fft.py``) or  as an app with an input file (``impactx input_cfchannel_10nC_fft.in``).
 Each can also be prefixed with an `MPI executor <https://www.mpi-forum.org>`__, such as ``mpiexec -n 4 ...`` or ``srun -n 4 ...``, depending on the system.
 
+We also provide the same example with the multi-grid (MLMG) Poisson solver.
+
 .. tab-set::
 
-   .. tab-item:: Python Script
+   .. tab-item:: Python Script (FFT)
+
+       .. literalinclude:: run_cfchannel_10nC_fft.py
+          :language: python3
+          :caption: You can copy this file from ``examples/cfchannel/run_cfchannel_10nC_fft.py``.
+
+   .. tab-item:: Python Script (MLMG)
 
-       .. literalinclude:: run_cfchannel_10nC.py
+       .. literalinclude:: run_cfchannel_10nC_mlmg.py
           :language: python3
-          :caption: You can copy this file from ``examples/cfchannel/run_cfchannel_10nC.py``.
+          :caption: You can copy this file from ``examples/cfchannel/run_cfchannel_10nC_mlmg.py``.
+
+   .. tab-item:: App Input File (FFT)
+
+       .. literalinclude:: input_cfchannel_10nC_fft.in
+          :language: ini
+          :caption: You can copy this file from ``examples/cfchannel/input_cfchannel_10nC_fft.in``.
 
-   .. tab-item:: App Input File
+   .. tab-item:: App Input File (MLMG)
 
-       .. literalinclude:: input_cfchannel_10nC.in
+       .. literalinclude:: input_cfchannel_10nC_mlmg.in
           :language: ini
-          :caption: You can copy this file from ``examples/cfchannel/input_cfchannel_10nC.in``.
+          :caption: You can copy this file from ``examples/cfchannel/input_cfchannel_10nC_mlmg.in``.
 
 
 Analyze

examples/expanding_beam/README.rst

@@ -25,24 +25,38 @@ Run
 
 This example can be run **either** as:
 
-* **Python** script: ``python3 run_expanding.py`` or
-* ImpactX **executable** using an input file: ``impactx input_expanding.in``
+* **Python** script: ``python3 run_expanding_fft.py`` or
+* ImpactX **executable** using an input file: ``impactx input_expanding_fft.in``
 
 For `MPI-parallel <https://www.mpi-forum.org>`__ runs, prefix these lines with ``mpiexec -n 4 ...`` or ``srun -n 4 ...``, depending on the system.
 
+We also provide the same example with the multi-grid (MLMG) Poisson solver.
+
 .. tab-set::
 
-   .. tab-item:: Python: Script
+   .. tab-item:: Python: Script (FFT)
+
+      .. literalinclude:: run_expanding_fft.py
+         :language: python3
+         :caption: You can copy this file from ``examples/expanding/run_expanding_fft.py``.
+
+   .. tab-item:: Python: Script (MLMG)
 
-      .. literalinclude:: run_expanding.py
+      .. literalinclude:: run_expanding_mlmg.py
          :language: python3
-         :caption: You can copy this file from ``examples/expanding/run_expanding.py``.
+         :caption: You can copy this file from ``examples/expanding/run_expanding_mlmg.py``.
+
+   .. tab-item:: Executable: Input File (FFT)
+
+       .. literalinclude:: input_expanding_fft.in
+          :language: ini
+          :caption: You can copy this file from ``examples/expanding/input_expanding_fft.in``.
 
-   .. tab-item:: Executable: Input File
+   .. tab-item:: Executable: Input File (MLMG)
 
-       .. literalinclude:: input_expanding.in
+       .. literalinclude:: input_expanding_mlmg.in
           :language: ini
-          :caption: You can copy this file from ``examples/expanding/input_expanding.in``.
+          :caption: You can copy this file from ``examples/expanding/input_expanding_mlmg.in``.
 
 
 Analyze