code: def _get_filename(self, key, filename):
          
          with open(filename, 'wb') as dest:
              return self._get_file(key, dest)
docs: Write key to file. Either this method or
          :meth:`~simplekv.KeyValueStore._get_file` will be called by
          :meth:`~simplekv.KeyValueStore.get_file`. This method only accepts
          filenames and will open the file with a mode of ``wb``, then call
          :meth:`~simplekv.KeyValueStore._get_file`.
  
          :param key: Key to be retrieved
          :param filename: Filename to write to