@staticmethod
def bind_collection_to_model_cls(cls):
    """Bind collection to model's class.

        If collection was not specialized in process of model's declaration,
        subclass of collection will be created.
        """
    cls.Collection = type('{0}.Collection'.format(cls.__name__), (cls.
        Collection,), {'value_type': cls})
    cls.Collection.__module__ = cls.__module__
