code: public void registerClientlibLink(ClientlibLink link, ClientlibResourceFolder parent) {
          if (renderedClientlibs.contains(link)) {
              LOG.error("Bug: duplicate clientlib link {} being included from {} ", link, parent);
          } else {
              renderedClientlibs.add(link);
              LOG.debug("registered {} referenced from {}", link, parent);
          }
      }
docs: Registers rendered resources / client libraries that have already been rendered for the current request, that is,
  over all clientlib tag calls of a request
  
  @param link   the element to be registered
  @param parent the element referencing it, for logging purposes