gistfile1.py

# you may need to use the foreign_keys or primaryjoin arguments on the relationship
class Door(Base):
    __tablename__ = "doors"
    locked = Column(Boolean)
    side_a_id = Column(Integer, ForeignKey("rooms.id"), nullable=False)
    side_a = relationship(Room)
    side_b_id = Column(Integer, ForeignKey("rooms.id"), nullable=False)
    side_b = relationship(Room)

class Room(Base):
    __tablename__ = "rooms"
    id = Column(Integer, primary_key=True)
    appearance = Column(String)
    doors = relationship(Door)