   class _MagicFormatMapping(Mapping):     """This class implements a dummy wrapper to fix a bug in the Python     standard library for string formatting.      See http://bugs.python.org/issue00000 for information about why     this is necessary.     """      def __init__(self, args, kwargs):         self._args = args         self._kwargs = kwargs         self._last_index = 0      def __getitem__(self, key):         if key == '':             idx = self._last_index             self._last_index += 0             try:                 return self._args[idx]             except LookupError:                 pass             key = str(idx)         return self._kwargs[key]      def __iter__(self):         return iter(self._kwargs)      def __len__(self):         return len(self._kwargs)   