code: def wrap(self, starter_cls):
          
          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)
docs: If starter_cls is not a ProcessStarter, assume it's the legacy
          preparefunc and return it bound to a CompatStarter.