def METHOD_NAME() -> LegacyKeyring:
    if sys.platform == "darwin":
        return cast(Callable[[], LegacyKeyring], MacKeyring)()
    elif sys.platform == "win32" or sys.platform == "cygwin":
        return cast(Callable[[], LegacyKeyring], WinKeyring)()
    elif sys.platform == "linux":
        keyring: CryptFileKeyring = CryptFileKeyring()
        keyring.keyring_key = "your keyring password"
        return keyring
    raise click.ClickException(f"platform '{sys.platform}' not supported.")