Render each of the collision objects onto the specified surface.

def draw(self, milliseconds, surface):
        """Render each of the collision objects onto the specified surface."""
        if self.is_visible:
            global collidable_objects
            for obj in collidable_objects:
                if obj.is_visible:
                    obj.draw(milliseconds, surface)
            super(CollisionManager, self).draw(milliseconds, surface)