docs: def generate_session_id(data):
      """
      Generate session ID based on HOST, TTY, PID [#]_ and start time.
  
      :type data: dict
      :rtype: str
  
      .. [#] PID of the shell, i.e., PPID of this Python process.
  
      """
      host = data['environ']['HOST']
      tty = data['environ'].get('TTY') or 'NO_TTY'
      return ':'.join(map(str, [
          host, tty, os.getppid(), data['start']]))