Return cell at *row_idx*, *col_idx*.

        Return value is an instance of |_Cell|. *row_idx* and *col_idx* are
        zero-based, e.g. cell(0, 0) is the top, left cell in the table.

def cell(self, row_idx, col_idx):
        """Return cell at *row_idx*, *col_idx*.

        Return value is an instance of |_Cell|. *row_idx* and *col_idx* are
        zero-based, e.g. cell(0, 0) is the top, left cell in the table.
        """
        return _Cell(self._tbl.tc(row_idx, col_idx), self)