@classmethod
def get_polymorphic_serializer_for_instance(cls, instance):
    """
        Return the polymorphic serializer associated with the given instance/model.
        Raise `NotImplementedError` if no serializer is found for the given model. This usually
        means that a serializer is missing in the class's `polymorphic_serializers` attribute.
        """
    try:
        return cls._poly_model_serializer_map[instance._meta.model]
    except KeyError:
        raise NotImplementedError(
            'No polymorphic serializer has been found for model {}'.format(
            instance._meta.model.__name__))
