'Insert a child canvas widget before a given index.
:type child: CanvasWidget
:param child: The canvas widget that should be inserted.
:type index: int
:param index: The index where the child widget should be
inserted.  In particular, the index of ``child`` will be
``index``; and the index of any children whose indices were
greater than equal to ``index`` before ``child`` was
inserted will be incremented by one.'

def insert_child(self, index, child):

    self._children.insert(index, child)
    self._add_child_widget(child)
