def METHOD_NAME(mb_refstate: Optional[str]) -> bool:
    """
    MBA API front-end for checking the validity of a MBA policy (aka refstate).
    :param mb_refstate: a string describing the policy
    :returns: true if the string is valid policy
    """
    try:
        m = _find_implementation("policy_is_valid")
        return m.METHOD_NAME(mb_refstate)  # type: ignore[no-any-return]
    except Exception as e:
        raise ValueError from e