code: @Override
      public List<KeyedMessageWithType> invokeOutput(final Mp instance) throws DempsyException {
          try {
              return Arrays.asList(Optional.ofNullable(instance.output()).orElse(EMPTY_KEYED_MESSAGE_WITH_TYPE));
          } catch(final RuntimeException rte) {
              throw new DempsyException(rte, true);
          }
      }
docs: This lifecycle phase is implemented by invoking the {@link Mp#output()} method on the instance
  
  @see MessageProcessorLifecycle#invokeOutput(Object)