code: def mean_length(self):
      if self.lenbuffer:
          return np.mean(self.lenbuffer)
      else:
          return 0
  
imports: import os
  import numpy
  import tensorflow
  from collections import deque
label_desc: Use image node_id 3 for calling the EpisodeStats obj's underlying member method code with example usage: obj.mean_length() and returns: np, int