Ast type hints

[ilnarkhasanov]

Closes #171

[yegor256]

@ilnarkhasanov is it possible to configure pylint or maybe some other code analysis tool such that it catches Python code without type hints? If we add such a tool to the build, it will help us avoid similar problems in the future.

[yegor256]

@ilnarkhasanov maybe you can just add mypy to our existing lint.sh script, where we call pylint. There is no need to create a separate Github Actions job, I believe.

[ilnarkhasanov]

@yegor256 I have added mypy to the lint.sh. Could you check, please?

[yegor256]

@rultor merge

[rultor]

@rultor merge

@yegor256 OK, I'll try to merge now. You can check the progress of the merge here

[rultor]

@rultor merge

@yegor256 Done! FYI, the full log is here (took me 15min)

[yegor256]

@ilnarkhasanov thanks!