class_docstr: Measure elapesed time via 'with' context.
code: def __init__(self, msg=""):
      self.msg = msg
      self.t = None
  
file_path: BigDL/python/friesian/example/recall/utils.py
imports: import time
  import os
  import multiprocessing
label_desc: Use image node_id 1 to create a new StopWatch object  with example: obj = StopWatch(msg)