code: public static <T extends Request> Predicate<HandlerInput> requestType(Class<T> requestType) {
          return i -> requestType.isInstance(i.getRequestEnvelope().getRequest());
      }
docs: Returns a predicate that returns to true if the incoming request is an instance
  of the given request class.
  @param <T> class of the request to evaluate against
  @param requestType request type to evaluate against
  @return true if the incoming request is an instance of the given request class