def create_closure_model(cls):
    """Creates a <Model>Closure model in the same module as the model."""
    meta_vals = {
        'unique_together':  (("parent", "child"),)
    }
    if getattr(cls._meta, 'db_table', None):
        meta_vals['db_table'] = '%sclosure' % getattr(cls._meta, 'db_table')
    model = type('%sClosure' % cls.__name__, (models.Model,), {
        'parent': models.ForeignKey(
            cls.__name__,
            related_name=cls.closure_parentref()
        ),
        'child': models.ForeignKey(
            cls.__name__,
            related_name=cls.closure_childref()
        ),
        'depth': models.IntegerField(),
        '__module__':   cls.__module__,
        '__unicode__': _closure_model_unicode,
        'Meta': type('Meta', (object,), meta_vals),
    })
    setattr(cls, "_closure_model", model)
    return model