def _index(self):
        """Keys a list of file paths that have been pickled in this directory.
        The index is stored in a json file in the same directory as the 
        pickled objects."""
        if self.__index is None:
            try:
                with open(self._get_path('index.json')) as f:
                    data = json.load(f)
            except (IOError, ValueError):
                self.__index = {}
            else:
                # 0 means version is not defined (= always delete cache):
                if data.get('version', 0) != self.version:
                    self.clear_cache()
                    self.__index = {}
                else:
                    self.__index = data['index']
        return self.__index
def _index ( self ) : if self . __index is None : try : with open ( self . _get_path ( 'index.json' ) ) as f : data = json . load ( f ) except ( IOError , ValueError ) : self . __index = { } else : if data . get ( 'version' , 0 ) != self . version : self . clear_cache ( ) self . __index = { } else : self . __index = data [ 'index' ] return self . __index
Keys a list of file paths that have been pickled in this directory.
        The index is stored in a json file in the same directory as the 
        pickled objects.