Add more Python type hints and add mypy valitations. This validation could be a step in GH actions or tox You can learn more about type hints in this [link](https://docs.python.org/3/library/typing.html) [Mypy](https://mypy.readthedocs.io/en/stable/command_line.html) has a command line checker: ``` mypy pyms ``` Ideally, mypy must return 0 errors, but could be a hard work because pyms create dynamic attributes.
