Shared via mypy Playground

main.py

from typing import overload, Literal

@overload
def execute_command(command: str,
                    additional_arguments: str = '',
                    *,
                    capture_output: Literal[True],
                    ) -> str:
    ...

@overload
def execute_command(command: str,
                    additional_arguments: str = '',
                    capture_output: Literal[False] = False,
                    ) -> None:
    ...

def execute_command(command, additional_arguments='', capture_output=False):
    if capture_output:
        return ''