code: def _combine_attr_fast_update(self, attr, typ):
          '''Avoids having to call _update for each intermediate base.  Only
          works for class attr of type UpdateDict.
  
          '''
          values = dict(getattr(self, attr, {}))
          
          for base in self._class_data.bases:
              vals = dict(getattr(base, attr, {}))
              preserve_attr_data(vals, values)
              values = combine(vals, values)
              
          setattr(self, attr, typ(values)f _combine_attr_fast_update(self, attr, typ):
          '''Avoids having to call _update for each intermediate base.  Only
          works for class attr of type UpdateDict.
  
          '''
          values = dict(getattr(self, attr, {}))
          
          for base in self._class_data.bases:
              vals = dict(getattr(base, attr, {}))
              preserve_attr_data(vals, values)
              values = combine(vals, values)
              
          setattr(self, attr, typ(values))
docs: Avoids having to call _update for each intermediate base.  Only
          works for class attr of type UpdateDict.