class Group(Base):
    __tablename__ = 'groups'
id = Column(Integer, primary_key=True)
users = relationship('User', secondary=users_groups, lazy='select', backref
    ='groups')
users_dynamic = relationship('User', passive_deletes=True, secondary=
    users_groups, lazy='dynamic')
SQLAlchemy DELETE Error caused by having a both lazy-load AND a dynamic version of the same relationship