SQLAlchemy 2.0 新特性
Migrating an Existing Mapping
Step one - declarative_base() is superseded by DeclarativeBase
Step two - replace Declarative use of Column with mapped_column()
Step three - apply exact Python types as needed using Mapped
Step four - remove mapped_column() directives where no longer needed
A mapped_column() directive with no parameters can be removed entirely.
fullname: Mapped[Optional[str]]
