Shared via mypy Playground

main.py

from typing import TypeVar, Generator
from types import coroutine

T = TypeVar("T", str, bytes)

async def process(data: T) -> T:
    return data

@coroutine    
def process2(data: T) -> Generator[T, None, T]:
    yield data
    return data

async def _typecheck() -> None:
    reveal_type(process)
    reveal_type(await process("hello"))
    reveal_type(await process(b"bytes"))
    # reveal_type(await process(1))  # correctly rejected
    
reveal_type(process2)
reveal_type(process2("hello"))
reveal_type(process2(b"bytes"))