code: public static <I> JMSubscriber<I> getJsonStringSOPLSubscriber(
              Function<I, ?> transformFunction) {
          return getSOPLSubscriber(
                  o -> JMJson.toJsonString(transformFunction.apply(o)));
      }
docs: Gets json string sopl subscriber.
  
  @param <I>               the type parameter
  @param transformFunction the transform function
  @return the json string sopl subscriber