Someone

link_table = Table('link', metadata,    Column('from_user_id', types.Integer, ForeignKey('user.id'), nullable=False),    Column('to_user_id', types.Integer, ForeignKey('user.id'), nullable=False),)                   user_mapper = mapper(User, user_table, properties = {    'characters': relation(Character, backref='user'),    'links': relation(User, secondary='link_table',                      primaryjoin = user_table.c.id == link_table.c.from_user_id,                      secondaryjoin = user_table.c.id == link_table.c.to_user_id)})