code: public void processMessage(MessageEnvelope envelope) {
  		
  		for (ActionFrame f : this.actionFrameList) {
  			// If the policy is FIRST_ONLY stop processing the chain at the
  			// first trigger.
  			this.envelope = new MessageEnvelope();
  			if (f.getReplies() != null && f.getReplies().size() > 0) {
  				if (f.processMultipleReply(envelope)
  						&& this.botMillPolicy.equals(BotMillPolicy.FIRST_ONLY)) {
  					break;
  				}
  			} else {
  				if (f.process(envelope)
  						&& this.botMillPolicy.equals(BotMillPolicy.FIRST_ONLY)) {
  					break;
  				}
  			}
  		}
  	}
docs: Checks if there's any registered {@link FbBotMillEvent} for the incoming
  callback. If there's any, then the callback is handled. The chain will be
  processed according to the {@link BotMillPolicy} followed by this bot. If
  the policy is {@link BotMillPolicy#FIRST_ONLY}, the chain will be
  processed until the first callback matches. Otherwise, if the policy is
  {@link BotMillPolicy#PROCESS_ALL}, all the chain will always be
  processed.
  
  @param envelope
  the incoming message.