':return: A bounding box for this ``CanvasWidget``. The bounding
box is a tuple of four coordinates, *(xmin, ymin, xmax, ymax)*,
for a rectangle which encloses all of the canvas
widget\'s graphical elements.  Bounding box coordinates are
specified with respect to the coordinate space of the ``Canvas``.
:rtype: tuple(int, int, int, int)'

def bbox(self):

    if self.__hidden:
        return (0, 0, 0, 0)
    if (len(self.tags()) == 0):
        raise ValueError('No    tags')
    return self.__canvas.bbox(*self.tags())
