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