'Create a new container widget.  This constructor should only
be called by subclass constructors.
:type canvas: Tkinter.Canvas
:param canvas: This canvas widget\'s canvas.
:param child: The container\'s child widget.  ``child`` must not
have a parent.
:type child: CanvasWidget
:param attribs: The new canvas widget\'s attributes.'

def __init__(self, canvas, child, **attribs):

    self._child = child
    self._add_child_widget(child)
    CanvasWidget.__init__(self, canvas, **attribs)
