Remove TSchema and add __call__ method to resolve #322

[mutricyl]

#322 raised that mypy showed error when using Use inside And and during investigation mixing Or and And also showed an issue.

1. I have added an empty __call__ function to class Use to make sure that mypy considers it as Callable
2. I got rid of TSchema and brought class Schema on top of the file as it appends that mypy is not so good with Generics[]

I am updating Regex as well to make it mypy Callable.

Closes #322