docs: def _to_dict(self):
          """Return a json dictionary representing this model."""
          _dict = {}
          if hasattr(self, 'width') and self.width is not None:
              _dict['width'] = self.width
          if hasattr(self, 'height') and self.height is not None:
              _dict['height'] = self.height
          if hasattr(self, 'left') and self.left is not None:
              _dict['left'] = self.left
          if hasattr(self, 'top') and self.top is not None:
              _dict['top'] = self.top
          return _dict