Class A

test/ext/test_mutable.py:255–262

        """test #9676"""

        class A(decl_base):
            __tablename__ = "a"

            id: Mapped[int] = mapped_column(primary_key=True)

            json: Mapped[Dict[str, Any]] = mapped_column(
                MutableDict.as_mutable(JSON())
            )

        class B(A):
            pass