code: public int signal(int signal, String arg)
  	throws GramException, GSSException {
  	return Gram.jobSignal(this, signal, arg);
      }
docs: Sends a signal command to the job.
  
  @param signal signal type
  @param arg    argument of signal
  @throws GramException
  if error occurs during signalization.
  @throws GSSException
  if user credentials are invalid.