code: private List<ResourceBuilderModel> getRegisteredListForResource(ResourceModel resource) {
          if(resourceIDs.containsKey(resource.getResourceID())) {
              return resourceIDs.get(resource.getResourceID());
          } else {
              LinkedList<ResourceBuilderModel> tempList = new LinkedList<>();
              resourceIDs.put(resource.getResourceID(), tempList);
              return tempList;
          }
      }
docs: returns the list with all the ResourceBuilders listening to the Resource
  @param resource the resource to listen to
  @return a List of ResourceBuilders