code: private SpeechletRequestHandler getRequestStreamHandler() {
          final Set<String> supportedApplicationIds = getSupportedApplicationIds();
          // at least one supported application-id need to be provided
          Validate.notEmpty(supportedApplicationIds, "Must provide supported application-id either with overriding the getter or using AlexaApplication-annotation in " + this.getClass().getSimpleName());
  
          return new SpeechletRequestHandler(
                  Collections.singletonList(
                          new ApplicationIdSpeechletRequestVerifier(supportedApplicationIds)),
                  Arrays.asList(
                          new ResponseSizeSpeechletResponseVerifier(),
                          new OutputSpeechSpeechletResponseVerifier(),
                          new CardSpeechletResponseVerifier()));
      }
docs: Constructs the stream handler giving it all the provided information.
  @return stream handler