class_docstr: A time stat for logging the elapsed time of code running
  
  Example:
      time_stat = TimeStat()
      with time_stat:
          // some code
      print(time_stat.mean)
code: def mean(self):
      return self.time_samples.mean
  
file_path: PARL/parl/utils/time_stat.py
imports: import time
  from parl.utils.window_stat import WindowStat
label_desc: Use image node_id 4 for calling the TimeStat obj's underlying member method code with example usage: obj.mean() and returns: self