def METHOD_NAME(credentials: Credentials) -> Optional[str]:
    secret = credentials.secret
    if not secret:
        return secret
    if isinstance(secret, Password):
        plaintext_secret = get_plaintext(secret.password)
        return plaintext_secret
    if isinstance(secret, LMHash):
        plaintext_secret = get_plaintext(secret.lm_hash)
        return f"{plaintext_secret}:00000000000000000000000000000000"
    if isinstance(secret, NTHash):
        plaintext_secret = get_plaintext(secret.nt_hash)
        return f"00000000000000000000000000000000:{plaintext_secret}"
    raise ValueError(f"Unknown secret type {type(secret)}")