code: protected void recordContentLoader(final String patchID, final PatchContentLoader contentLoader) {
          if (contentLoaders.containsKey(patchID)) {
              throw new IllegalStateException("Content loader already registered for patch " + patchID); // internal wrong usage, no i18n
          }
          contentLoaders.put(patchID, contentLoader);
      }
docs: Record a content loader for a given patch id.
  
  @param patchID       the patch id
  @param contentLoader the content loader