code: def write_pid(pidfile):
      
      pid = str(os.getpid())
      try:
          with open(pidfile, mode='w') as _file:
              print("writing processID {p} to pidfile".format(p=pid))
              _file.write(pid)
      except OSError as exc:
          sys.exit("failed to write pidfile:{e}".format(e=exc))
docs: Write processID to the pidfile.
  
      Notice:
          It exits main program if it fails to write pidfile.
  
      Arguments:
          pidfile (str): pidfile to update