如何使用sql.alchemy.orm.validates验证来自不同表的表字段？

from sqlalchemy import Column, Integer, String, ForeignKey
from sqlalchemy.orm import relationship, validates
from sqlalchemy.ext.declarative import declarative_base

Base = declarative_base()

class Table1(Base):
    __tablename__ = 'table1'
    id = Column(Integer, primary_key=True)
    name = Column(String)
    table2_id = Column(Integer, ForeignKey('table2.id'))
    table2 = relationship('Table2')

class Table2(Base):
    __tablename__ = 'table2'
    id = Column(Integer, primary_key=True)
    value = Column(Integer)

class Table1(Base):
    # ...

    @validates('name')
    def validate_name(self, key, name):
        if len(name) < 5:
            raise ValueError('Name must be at least 5 characters long.')
        return name

    @validates('table2')
    def validate_table2(self, key, table2):
        if table2.value < 10:
            raise ValueError('Table2 value must be greater than or equal to 10.')
        return table2

table1 = Table1(name='Test', table2=Table2(value=15))
session.add(table1)
session.commit()