SAWarning:对于延迟加载的属性的相似性,多行返回uselist=False。tag1'

我从SQLAlchemy得到以下警告,我想知道问题是什么:

\venv\lib\site-packages\sqlalchemy\orm\strategies.py:911: SAWarning: Multiple rows returned with uselist=False for lazily-loaded attribute 'Similarity.tag1' 
  util.warn(
\venv\lib\site-packages\sqlalchemy\orm\strategies.py:911: SAWarning: Multiple rows returned with uselist=False for lazily-loaded attribute 'Similarity.tag' 
  util.warn(

我的ORM类如下所示:

class Similarity(db.Model):
    __tablename__ = 'similarities'

    tag_id_1 = db.Column(db.ForeignKey('tags.id'), primary_key=True, nullable=False)
    tag_id_2 = db.Column(db.ForeignKey('tags.id'), primary_key=True, nullable=False, index=True)
    value = db.Column(DOUBLE, nullable=False)

    tag = db.relationship('Tag', primaryjoin='Similarity.tag_id_1 == Tag.id', backref='tag_similarities')
    tag1 = db.relationship('Tag', primaryjoin='Similarity.tag_id_2 == Tag.id', backref='tag_similarities_0')


class Tag(db.Model):
    __tablename__ = 'tags'

    id = db.Column(db.Integer, primary_key=True, nullable=False, autoincrement=True)
    language_id = db.Column(db.ForeignKey('languages.id'), primary_key=True, nullable=False, index=True)
    name = db.Column(db.String(45), nullable=False, index=True)

    language = db.relationship('Language', primaryjoin='Tag.language_id == Language.id', backref='tags')

我用 SQLAlchemy 1.3.22 以及Python 3.8。你能解释一下这条信息是关于什么的吗?我怎样才能解决这个问题?