Returns the middle point of the bounding box

        :return: middle point
        :rtype: (float, float)

def middle(self):
        """ Returns the middle point of the bounding box

        :return: middle point
        :rtype: (float, float)
        """
        return (self.min_x + self.max_x) / 2, (self.min_y + self.max_y) / 2