Possibly implementations of os.fspath()

fspath.py

# str-only.
def fspath(path):
    try:
        path = path.__fspath__()
    except AttributeError:
        pass
    if isinstance(path, str):
        return path
    else:
        raise TypeError


# Default to str, bytes allowed only when an argument.
def fspath(path, *, allow_bytes=False):
    if allow_bytes and isinstance(path, bytes):
        return path
    try:
        path = path.__fspath__()
    except AttributeError:
        pass
    if isinstance(path, str):
        return path
    else:
        raise TypeError


# Default to str, bytes allowed from anywhere.
def fspath(path, *, allow_bytes=False):
    try:
        path = path.__fspath__()
    except AttributeError:
        pass
    if isinstance(path, str):
        return path
    elif allow_bytes and isinstance(path, bytes):
        return path
    else:
        raise TypeError


# str or bytes allowed.
def fspath(path):
    try:
        path = path.__fspath__()
    except AttributeError:
        pass
    if isinstance(path, (str, bytes)):
        return path
    else:
        raise TypeError