The arguments it takes ... like an integer or a float, or container objects you know aren’t going to have many elements. You can also accept Python-native types at the function boundary, and ...

It's important to remember that Python ... [int]: first = 0 second = 1 while True: yield first first, second = second, first+second But if you try to run Mypy, you get the following: atf201906b.py:6: ...