[Python] sqlalchemy - clear list and add item - null violation for foreign key

I try to clear a list and add an item to it. I get IntegrityError('(psycopg2.errors.NotNullViolation) null value in column "game_id" of relation "player" violates not-null co...2, null).\n')

class Game(Base):
__tablename__ = "game"
game_id: int = Column(INTEGER, primary_key=True, server_default=Identity(always=True, start=1, increment=1, minvalue=1, maxvalue=2147483647, cycle=False, cache=1), autoincrement=True)
players = relationship('Player', back_populates='game')

class Player(Base):
__tablename__ = "player"
player_id: int = Column(INTEGER, primary_key=True, server_default=Identity(always=True, start=1, increment=1, minvalue=1, maxvalue=2147483647, cycle=False, cache=1), autoincrement=True)
game_id: int = Column(INTEGER, ForeignKey('game.game_id'), nullable=False)
game = relationship('Game', back_populates='players')


game = session.query(Game).first()
game.players.clear()
player = Player(name='john')
game.players.append(player)
session.commit()

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