def add_distances(self, indices, periodic=True, indices2=None):
        r
        from .distances import DistanceFeature
        atom_pairs = _parse_pairwise_input(
            indices, indices2, self.logger, fname='add_distances()')
        atom_pairs = self._check_indices(atom_pairs)
        f = DistanceFeature(self.topology, atom_pairs, periodic=periodic)
        self.__add_feature(f)