And the type hints and behaviour are specified as part of Python, so it's kind of baked in. It's just that the actual type checker is not part of CPython, though Mypy is considered the reference implementation.

We have quite a large code base and very few `# type: ignore[code]` directives.

Some third party code still has poor type hints, but for the most part it's fine, and we get null safety which you don't get for Java.