I have a function like this:

def run_process(path: str, *args: str) -> dict:

    cmd = subprocess.run(
        ["command", *args, path],
        capture_output=True,
    )

    ret = {
        "stdout": cmd.stdout.decode("utf-8"),
        "stderr": cmd.stderr.decode("utf-8"),
        "returncode": cmd.returncode,
    }

    return ret

I’m trying to add a complete type hint for the ret dict. I tried Dict[str, Union[str, int]]

But mypy has some issues with this:

error: Incompatible return value type (got "Dict[str, object]", expected "Dict[str, Union[str, int]]")  [return-value]

If I try to use it as run_process["stderr"].splitlines(), mypy says:

error: Item "int" of "Union[str, int]" has no attribute "splitlines"

How would I solve this?