'Add a new canvas widget to the scroll-watcher.  The
scroll-watcher will ensure that the new canvas widget is
always contained in its canvas\'s scrollregion.
:param canvaswidget: The new canvas widget.
:type canvaswidget: CanvasWidget
:rtype: None'

def add_child(self, canvaswidget):

    self._add_child_widget(canvaswidget)
    self.update(canvaswidget)
