def subframe(self, rowids):
        """Return a new frame whose columns are subcolumns of this frame.

        The given row IDs should be within range [0, self.num_rows), and allow
        duplicate IDs.

        Parameters
        ----------
        rowids : Tensor
            Row IDs

        Returns
        -------
        Frame
            A new subframe.
        """
        subcols = {k: col.subcolumn(rowids) for k, col in self._columns.items()}
        subf = Frame(subcols, len(rowids))
        subf._initializers = self._initializers
        subf._default_initializer = self._default_initializer
        return subf
Return a new frame whose columns are subcolumns of this frame.

        The given row IDs should be within range [0, self.num_rows), and allow
        duplicate IDs.

        Parameters
        ----------
        rowids : Tensor
            Row IDs

        Returns
        -------
        Frame
            A new subframe.
        
python/dgl/frame.py