code: public Collection<File> getResources(List<String> extensions) {
          List<File> files = new ArrayList<>();
          files.addAll(WatcherUtils.getAllFilesFromDirectory(getInternalAssetsDirectory(), extensions));
          files.addAll(WatcherUtils.getAllFilesFromDirectory(getExternalAssetsDirectory(), extensions));
          return files;
      }
docs: Finds all resources from internal and external assets directories having one of the specified extensions.
  
  @param extensions the extensions
  @return the set of file, potentially empty if no files match.