gistfile1.py

# What I have
following = db.relationship('User',
                            secondary=UserFollowing.__table__,
                            primaryjoin='User.id==UserFollowing.user1_id',
                            secondaryjoin='User.id==UserFollowing.user2_id',
                            foreign_keys=[UserFollowing.user1_id, UserFollowing.user2_id],
                            lazy='joined')


# What I want
following = db.relationship('User',
                            secondary=UserFollowing.__table__,
                            primaryjoin='and_(User.id==UserFollowing.user1_id, remote(User.id==UserFollowing.user1_id))',
                            foreign_keys='[UserFollowing.user1_id]',
                            lazy='joined')

# Error:
# InvalidRequestError: One or more mappers failed to initialize - can't proceed with initialization of other mappers.  Original exception was: Relationship User.following could not determine any unambiguous local/remote column pairs based on join condition and remote_side arguments.  Consider using the remote() annotation to accurately mark those elements of the join condition that are on the remote side of the relationship.