def wrap(self, starter_cls):
        """
        If starter_cls is not a ProcessStarter, assume it's the legacy
        preparefunc and return it bound to a CompatStarter.
        """
        if isinstance(starter_cls, type) and issubclass(starter_cls, ProcessStarter):
            return starter_cls
        depr_msg = 'Pass a ProcessStarter for preparefunc'
        warnings.warn(depr_msg, DeprecationWarning, stacklevel=3)
        return functools.partial(CompatStarter, starter_cls)