code: def _add_chart_graphicFrame(self, rId, x, y, cx, cy):
          
          shape_id = self._next_shape_id
          name = 'Chart %d' % (shape_id-1)
          graphicFrame = CT_GraphicalObjectFrame.new_chart_graphicFrame(
              shape_id, name, rId, x, y, cx, cy
          )
          self._spTree.append(graphicFrame)
          return graphicFrame
docs: Return new `p:graphicFrame` element appended to this shape tree.
  
          The `p:graphicFrame` element has the specified position and size and
          refers to the chart part identified by *rId*.