def mutable(self, message_class):

    if message_class.MESSAGE_TYPE_ID not in self.items:
      message = message_class()
      self.items[message_class.MESSAGE_TYPE_ID] = Item(message, message_class)
      return message
    item = self.items[message_class.MESSAGE_TYPE_ID]
    if not item.Parse(message_class):
      item.SetToDefaultInstance(message_class)
    return item.message
dataset/ETHPy150Open AppScale/appscale/AppServer/google/net/proto/message_set.py/MessageSet.mutable/original