code: def attr(self, *args):
          '''Add the specific attribute to the attribute dictionary
          with key ``name`` and value ``value`` and return ``self``.'''
          attr = self._attr
          if not args:
              return attr or {}
          result, adding = self._attrdata('attr', *args)
          if adding:
              for key, value in result.items():
                  if DATARE.match(key):
                      self.data(key[5:], value)
                  else:
                      if attr is None:
                          self._extra['attr'] = attr = {}
                      attr[key] = value
              result = self
          return resulf attr(self, *args):
          '''Add the specific attribute to the attribute dictionary
          with key ``name`` and value ``value`` and return ``self``.'''
          attr = self._attr
          if not args:
              return attr or {}
          result, adding = self._attrdata('attr', *args)
          if adding:
              for key, value in result.items():
                  if DATARE.match(key):
                      self.data(key[5:], value)
                  else:
                      if attr is None:
                          self._extra['attr'] = attr = {}
                      attr[key] = value
              result = self
          return result
docs: Add the specific attribute to the attribute dictionary
          with key ``name`` and value ``value`` and return ``self``.