code: def yield_tag(self, target=None, label=None):
          
          if target is None and label is None:
              raise ValueError('`target` and/or `label` must be specified')
          if label is None:
              return self._yield_from_target(target)
          if target is None:
              return self._yield_from_label(label)
          return self._yield_from_target_and_label(target, label)
docs: Returns a new Tag containing the bumped target and/or the bumped label