code: private IMessageProducer findRegisteredProducer(Class<?> clazz) {
          for (IMessageProducer producer : producers) {
              if (clazz.isInstance(producer)) {
                  return producer;
              }
          }
  
          return null;
      }
docs: Returns a producer of the specified class.
  
  @param clazz Class of the producer sought.
  @return The producer, or null if not found.