Python sqlalchemy.exc.IntegrityError不一致

当我删除子对象时，另一个对象的子字段为空。应该是这样的。如果仅删除依赖类对象，则应删除另一个。我应该假设如果我删除父对象，它下面的所有内容都应该被删除。从属对象、子对象以及其他对象（因为它与从属对象具有ondelete级联关系，并且从属对象与父对象具有ondelete级联关系）

当我删除父对象时，错误是抛出以下消息：

sqlalchemy.exc.IntegrityError:表“child”上的更新或删除违反了表“other”上的外键约束“other\u child\u id\u fkey” 详细信息：键（id）=（4）仍然从表“另一个”引用

当我删除子对象时，另一个类没有问题。为什么我会犯这个错误

class Parent():  

    id = Column(Integer ,primary_key = true)  
    children = relationship('Child', back_populates='parent', passive_deletes =True) 
    dependents = relationship('Dependent', back_populates='parent', passive_deletes =True)


class Child():  

   id = Column(Integer , primary_key = true)
   parent = relationship('Parent', back_populates='children')
   parent_id = Column(Integer, ForeignKey('parent.id', ondelete='CASCADE') 
   anothers = relationship('Another', back_populates='child') 


class Dependent():  

   id = Column(Integer , primary_key = true)
   parent = relationship('Parent', back_populates='children')
   parent_id = Column(Integer, ForeignKey('parent.id', ondelete='CASCADE') 
   another = relationship('Another', back_populates='dependent', uselist=False, passive_deletes = True) 


class Another():
   id = Column(Integer , primary_key = true)
  dependent = relationship('Dependent', back_populates='anothers')
  dependent_id = Column(Integer, ForeignKey('dependent.id', ondelete='CASCADE') 
  child = relationship('Child', back_populates='another')
  child_id = Column(Integer, ForeignKey('child.id'))