'Tuple defining the default ``bounding_box``.
``((y_low, y_high), (x_low, x_high))``'

@property
def bounding_box(self):

    dx = (self.x_width / 2)
    dy = (self.y_width / 2)
    return (((self.y_0 - dy), (self.y_0 + dy)), ((self.x_0 - dx), (self.x_0 + dx)))
