code: def _new_placeholder_table(self, rows, cols):
          
          shape_id, name, height = self.shape_id, self.name, Emu(rows*370840)
          return CT_GraphicalObjectFrame.new_table_graphicFrame(
              shape_id, name, rows, cols, self.left, self.top, self.width,
              height
          )
docs: Return a newly added `p:graphicFrame` element containing an empty
          table with *rows* rows and *cols* columns, positioned at the location
          of this placeholder and having its same width. The table's height is
          determined by the number of rows.