code: def get_needful_files(self):
          
          manifest = self.storage.load_manifest()
          if self.keep_unhashed_files:
              if PY3:
                  needful_files = set(manifest.keys() | manifest.values())
              else:
                  needful_files = set(manifest.keys() + manifest.values())
              needful_files = {self.storage.clean_name(file) for file in needful_files}
          else:
              needful_files = set(manifest.values())
          return {self.process_file(file) for file in needful_files}
docs: Returns currently used static files.
          Assumes that manifest staticfiles.json is up-to-date.