'Remove a hierarchical child widget.  This child will no longer
be considered part of this canvas widget for purposes of user
interaction.  ``_add_child_widget`` has two direct effects:
- It sets ``child``\'s parent to None.
- It removes ``child`` from the list of canvas widgets
returned by the ``child_widgets`` member function.
:param child: The child widget to remove.  ``child`` must be a
child of this canvas widget.
:type child: CanvasWidget'

def _remove_child_widget(self, child):

    self.__children.remove(child)
    child.__parent = None
