code: def create_new(cls, mapreduce_id, shard_number):
      
      shard_id = cls.shard_id_from_number(mapreduce_id, shard_number)
      state = cls(key_name=shard_id,
                  mapreduce_id=mapreduce_id)
      return state
docs: Create new shard state.
  
      Args:
        mapreduce_id: unique mapreduce id as string.
        shard_number: shard number for which to create shard state.
  
      Returns:
        new instance of ShardState ready to put into datastore.