如何用SQLAlchemy修改和合并列？

from sqlalchemy import create_engine, Column, Integer, String
from sqlalchemy.orm import sessionmaker
from sqlalchemy.ext.declarative import declarative_base

engine = create_engine('数据库连接字符串')
Session = sessionmaker(bind=engine)
session = Session()

Base = declarative_base()

class MyTable(Base):
    __tablename__ = 'my_table'
    id = Column(Integer, primary_key=True)
    column1 = Column(String)
    column2 = Column(String)
    # 其他列...

# 添加临时列
temp_column = Column(String)
MyTable.__table__.create_column(temp_column)

# 复制原有数据到临时列
session.query(MyTable).update({temp_column: MyTable.column1})

# 删除原有列
MyTable.__table__.c.column1.drop()

# 重命名临时列
temp_column.alter(name='column1')

# 合并列属性
session.query(MyTable).update({MyTable.column1: MyTable.column1 + MyTable.column2})

# 删除另一列
MyTable.__table__.c.column2.drop()

session.commit()
session.close()