def _delete(self, state=None):
        """Helper for :meth:`delete`

        Adds a delete mutation (for the entire row) to the accumulated
        mutations.

        ``state`` is unused by :class:`DirectRow` but is used by
        subclasses.

        :type state: bool
        :param state: (Optional) The state that is passed along to
                      :meth:`_get_mutations`.
        """
        mutation_val = data_v2_pb2.Mutation.DeleteFromRow()
        mutation_pb = data_v2_pb2.Mutation(delete_from_row=mutation_val)
        self._get_mutations(state).append(mutation_pb)