如何使用SQLalchemy正确设置关联表

from sqlalchemy import Column, Integer, String, ForeignKey
from sqlalchemy.orm import relationship

class User(Base):
    __tablename__ = 'users'
    id = Column(Integer, primary_key=True)
    name = Column(String)
    profile = relationship("Profile", uselist=False, back_populates="user")

class Profile(Base):
    __tablename__ = 'profiles'
    id = Column(Integer, primary_key=True)
    bio = Column(String)
    user_id = Column(Integer, ForeignKey('users.id'))
    user = relationship("User", back_populates="profile")

from sqlalchemy import Column, Integer, String, ForeignKey
from sqlalchemy.orm import relationship

class Department(Base):
    __tablename__ = 'departments'
    id = Column(Integer, primary_key=True)
    name = Column(String)
    employees = relationship("Employee", back_populates="department")

class Employee(Base):
    __tablename__ = 'employees'
    id = Column(Integer, primary_key=True)
    name = Column(String)
    department_id = Column(Integer, ForeignKey('departments.id'))
    department = relationship("Department", back_populates="employees")

from sqlalchemy import Column, Integer, String, Table, ForeignKey
from sqlalchemy.orm import relationship

association_table = Table('association', Base.metadata,
    Column('student_id', Integer, ForeignKey('students.id')),
    Column('course_id', Integer, ForeignKey('courses.id'))
)

class Student(Base):
    __tablename__ = 'students'
    id = Column(Integer, primary_key=True)
    name = Column(String)
    courses = relationship("Course", secondary=association_table, back_populates="students")

class Course(Base):
    __tablename__ = 'courses'
    id = Column(Integer, primary_key=True)
    name = Column(String)
    students = relationship("Student", secondary=association_table, back_populates="courses")