utils.py 文件源码

def check_reverse_relation(model, related_name):
    """
        Helper method to check if a given model related_name pair return a
        reverse relation instance that is associated by a ForeignKey.

        model: subclass of django.db.models.Model
        related_name: str
    """
    rel = get_reverse_relation(model, related_name)
    if rel is None:
        raise NotImplementedError(
            '{} does not have a reverse relation by the name "{}"'.format(
                model.__name__, related_name
            )
        )
    elif not isinstance(rel, ManyToOneRel):
        raise TypeError(
            'The reverse relation "{}" on {}.{} is not a ForeignKey.'
            'Timeseries only works with ForeignKey reverse relations.'.format(
                related_name, rel.field.model.__name__, rel.field.name
            )
        )

    return rel