Pair the geometrically equivalent atoms of the molecules.
        Calculate RMSD on all possible isomorphism mappings and return mapping
        with the least RMSD

        Args:
            mol1: First molecule. OpenBabel OBMol or pymatgen Molecule object.
            mol2: Second molecule. OpenBabel OBMol or pymatgen Molecule object.

        Returns:
            (list1, list2) if uniform atom order is found. list1 and list2
            are for mol1 and mol2, respectively. Their length equal
            to the number of atoms. They represents the uniform atom order
            of the two molecules. The value of each element is the original
            atom index in mol1 or mol2 of the current atom in uniform atom
            order.
            (None, None) if unform atom is not available.

def uniform_labels(self, mol1, mol2):
        """
        Pair the geometrically equivalent atoms of the molecules.
        Calculate RMSD on all possible isomorphism mappings and return mapping
        with the least RMSD

        Args:
            mol1: First molecule. OpenBabel OBMol or pymatgen Molecule object.
            mol2: Second molecule. OpenBabel OBMol or pymatgen Molecule object.

        Returns:
            (list1, list2) if uniform atom order is found. list1 and list2
            are for mol1 and mol2, respectively. Their length equal
            to the number of atoms. They represents the uniform atom order
            of the two molecules. The value of each element is the original
            atom index in mol1 or mol2 of the current atom in uniform atom
            order.
            (None, None) if unform atom is not available.
        """
        obmol1 = BabelMolAdaptor(mol1).openbabel_mol
        obmol2 = BabelMolAdaptor(mol2).openbabel_mol

        h1 = self.get_molecule_hash(obmol1)
        h2 = self.get_molecule_hash(obmol2)
        if h1 != h2:
            return None, None

        query = ob.CompileMoleculeQuery(obmol1)
        isomapper = ob.OBIsomorphismMapper.GetInstance(query)
        isomorph = ob.vvpairUIntUInt()
        isomapper.MapAll(obmol2, isomorph)

        sorted_isomorph = [sorted(x, key=lambda morp: morp[0])
                           for x in isomorph]
        label2_list = tuple([tuple([p[1] + 1 for p in x])
                             for x in sorted_isomorph])

        vmol1 = obmol1
        aligner = ob.OBAlign(True, False)
        aligner.SetRefMol(vmol1)
        least_rmsd = float("Inf")
        best_label2 = None
        label1 = list(range(1, obmol1.NumAtoms() + 1))
        # noinspection PyProtectedMember
        elements1 = InchiMolAtomMapper._get_elements(vmol1, label1)
        for label2 in label2_list:
            # noinspection PyProtectedMember
            elements2 = InchiMolAtomMapper._get_elements(obmol2, label2)
            if elements1 != elements2:
                continue
            vmol2 = ob.OBMol()
            for i in label2:
                vmol2.AddAtom(obmol2.GetAtom(i))
            aligner.SetTargetMol(vmol2)
            aligner.Align()
            rmsd = aligner.GetRMSD()
            if rmsd < least_rmsd:
                least_rmsd = rmsd
                best_label2 = copy.copy(label2)
        return label1, best_label2