code: def iter_doc_filepaths(self, **kwargs):  # pylint: disable=W0613
          
          with self._index_lock:
              for doc_id, info in self._doc_index.items():
                  if not self._is_alias(doc_id):
                      yield doc_id, info[-1]
docs: Returns a pair: (doc_id, absolute filepath of document file)
          for each document in this repository.
          Order is arbitrary.