code: def writejar(self, jar):
      
      if not jar or not isinstance(jar, string_types):
        raise ValueError('The jar path must be a non-empty string')
  
      self._jars.append(jar)
docs: Schedules all entries from the given ``jar``'s to be added to this jar save for the manifest.
  
      :param string jar: the path to the pre-existing jar to graft into this jar