Type Hinting/Type Checking/Type Enforcement

An optional feature in python, and even when used is not a strict enforcement.
Reveals issues when checked with python pip package tool mypy
Helps to do quick unit-tests.
you can use typing module for importing few types

#! python3
# filename: test.py

def add_these(a: int, b: int) -> int:
    return a + b
    
if __name__ == '__main__':
    print(add_these(1, 2))
    print(add_these('1', '2'))

Terminal

$ pip install mypy
$ mypy test.py