Represent data for the field.

def to_representation(self, obj):
        """ Represent data for the field. """
        many = isinstance(obj, collections.Iterable) \
            or isinstance(obj, models.Manager) \
            and not isinstance(obj, dict)

        assert self.serializer is not None \
            and issubclass(self.serializer, serializers.ModelSerializer), (
                "Bad serializer defined %s" % self.serializer
            )

        extra_params = {}
        if issubclass(self.serializer, ModelPermissionsSerializer):
            extra_params['cached_allowed_fields'] =\
                self.parent.cached_allowed_fields

        ser = self.serializer(obj, context=self.context, many=many,
                              **extra_params)
        return ser.data