code: def bbox(self):
          
          if not hasattr(self, '_bbox'):
              data = None
              for key in ('ARTBOARD_DATA1', 'ARTBOARD_DATA2', 'ARTBOARD_DATA3'):
                  if key in self.tagged_blocks:
                      data = self.tagged_blocks.get_data(key)
              assert data is not None
              rect = data.get(b'artboardRect')
              self._bbox = (
                  int(rect.get(b'Left')),
                  int(rect.get(b'Top ')),
                  int(rect.get(b'Rght')),
                  int(rect.get(b'Btom')),
              )
          return self._bbox
docs: (left, top, right, bottom) tuple.