How to use reveal_type in mypy
I found out in the end how to use it: You should just put and use the reveal_type in the code, and run it with the mypy program. Then, it will log a message that look like this:
Revealed type is 'builtins.str*'From the mypy documentation:
reveal_type is only understood by mypy and doesn’t exist in Python, if you try to run your program. You’ll have to remove any reveal_type calls before you can run your code. reveal_type is always available and you don’t need to import it.
For more reading: here.