@Internal
  @RequiresReadLock
  @RequiresBackgroundThread
  default @Nullable ContentUpdater contentUpdater(@NotNull DocumentationTarget target, @NotNull String url) {
    return null;
  }
@Internal
  @RequiresReadLock
  @RequiresBackgroundThread
  default @Nullable ContentUpdater contentUpdater(@NotNull DocumentationTarget target, @NotNull String url)