tester.py

from types import GenericAlias
from typing import get_type_hints


async def tester(param: list[str]):
    return [
        x + '!' for x in param
    ]


async def another_tester(param: str):
    return param + '!'

todo = ['a', 'b', 'c', 'd']

for task in [tester, another_tester]:
    params_class = list(get_type_hints(task).values())[0]
    batch_handler = type(params_class) is GenericAlias

    if batch_handler:
        task(todo)
    else:
        for x in todo:
            task(x)

async def another_tester(param: str) -> str:
    return param + '!'


async def tester(param: str | list[str]) -> list[str]:
    if isinstance(param, str):
        return [(await another_tester(param))]
    return [
        (await another_tester(param)) for x in param
    ]