Mypy (http://mypy-lang.org/) is the main tool for optional static type checking in Python. The idea is that, once you install it, it will analyze all of the files on your project, checking for inconsistencies on the use of the types. This is useful since, most of the time, it will detect actual bugs early, but sometimes it can give false positives.
You can install it with pip, and it is recommended to include it as a dependency for the project on the setup file:
$ pip install mypy
Once it is installed in the virtual environment, you just have to run the preceding command and it will report all of the findings on the type checks. Try to adhere to its report as much as possible, because most of the time, the insights ...
