def materialize_data(self):
        """Materialize the graph data on the current device.

        This method is a no-op if the graph data is already materialized.

        Returns
        -------
        DGLGraph
            The graph on the current device.
        """
        for frame in itertools.chain(self._node_frames, self._edge_frames):
            for col in frame._columns.values():
                col.data  # pylint: disable=pointless-statement
        return self
Materialize the graph data on the current device.

        This method is a no-op if the graph data is already materialized.

        Returns
        -------
        DGLGraph
            The graph on the current device.
        
python/dgl/heterograph.py