Checking ancestors

[kenneth-lee-ch]

In line 127 of the GraphUtils.py, how come the node is determined to be an ancestor once it is in z?

[zhi-yi-huang]

This method is to iteratively search for the parent node of the node in z. If the node is not in the current parent node, continue to search for its parent node. If it cannot be found until the queue is empty, then the node is not the ancestor node of the node in z.