boolean updateSingleIndex(@NotNull ID<?, ?> indexId,
                         @NotNull VirtualFile file,
                         int inputId,
                         @NotNull FileContent currentFC) {
    SingleIndexValueApplier<?> applier = createSingleIndexValueApplier(indexId, file, inputId, currentFC);
    if (applier != null) {
      return applier.apply();
    }
    else {
      return true;
    }
  }
boolean updateSingleIndex(@NotNull ID<?, ?> indexId,
                         @NotNull VirtualFile file,
                         int inputId,
                         @NotNull FileContent currentFC)