docs: def pid(self):
          """Get the pid which represents a daemonized process.
  
          The result should be None if the process is not running.
          """
          try:
  
              with open(self.pidfile, 'r') as pidfile:
  
                  try:
  
                      pid = int(pidfile.read().strip())
  
                  except ValueError:
  
                      return None
  
                  try:
  
                      os.kill(pid, 0)
  
                  except OSError as e:
  
                      if e.errno == errno.EPERM:
  
                          return pid
  
                      elif e.errno == errno.ESRCH:
  
                          return None
  
                      LOG.exception(
                          "os.kill returned unhandled error "
                          "{0}".format(e.strerror)
                      )
                      sys.exit(exit.PIDFILE_ERROR)
  
                  return pid
  
          except IOError:
  
              if not os.path.isfile(self.pidfile):
  
                  return None
  
              LOG.exception("Failed to read pidfile {0}.".format(self.pidfile))
              sys.exit(exit.PIDFILE_INACCESSIBLE)