It’s important to remember that Python, the language, isn’t changing,and it isn’t becoming statically typed. Mypy is a separate program, runningoutside Python, typically as part of a continuous integration (CI)system or invoked as part of a Git commit hook. The idea is that Mypyruns before you put your code into production, identifying where thedata doesn’t match the annotations you’ve made to your variables andfunction parameters.

Source: LXer – Python’s Mypy: Callables and Generators