Compare protein-protein interfaces of the structures of two pairs of
protein complexes and suporpose them.
:param model1: The model structure. If the superposition is successful, will
be superposed onto the reference structure
:type model1: :class:`~ost.mol.EntityView` or :class:`~ost.mol.EntityHandle`
:param model2: The reference structure
:type model2: :class:`~ost.mol.EntityView` or :class:`~ost.mol.EntityHandle`
:param ialign: If not None, the path to the ialign executable.
:returns: The result of the tmscore superposition
:rtype: :class:`iAlignResult`
:raises: :class:`~ost.settings.FileNotFound` if tmalign could not be located.
:raises: :class:`RuntimeError` if the superposition failed