code: def bounding_box(self):
          
          return (self._min_x, self._min_y, self._max_x, self._max_y)
docs: the bounding box of this SVG
          ``(min_x, min_y, max_x, max_y)``.
  
          .. code:: python
  
              svg_builder10x10.bounding_box = (0, 0, 10, 10)
              assert svg_builder10x10.bounding_box == (0, 0, 10, 10)
  
          ``viewBox``, ``width`` and ``height`` are computed from this.
  
          If the bounding box was never set, the result is a tuple of four
          :obj:`None`.