code: def _mean(items):
      """Return average (aka mean) for sequence of items."""
      return sum(items) / len(items)
  
imports: import random
  import warnings
  from abc import ABCMeta, abstractmethod
  from bisect import bisect
  from itertools import accumulate
  from nltk.lm.counter import NgramCounter
  from nltk.lm.util import log_base2
  from nltk.lm.vocabulary import Vocabulary
label_desc: Use image node_id 1 for calling a global function with example usage: _mean(items) and returns: unknown