docs: def _register_lltd_specific_class(*attr_types):
      """This can be used as a class decorator; if we want to support Python
      2.5, we have to replace
  
  @_register_lltd_specific_class(x[, y[, ...]])
  class LLTDAttributeSpecific(LLTDAttribute):
  [...]
  
  by
  
  class LLTDAttributeSpecific(LLTDAttribute):
  [...]
  LLTDAttributeSpecific = _register_lltd_specific_class(x[, y[, ...]])(
      LLTDAttributeSpecific
  )
  
      """
      def _register(cls):
          for attr_type in attr_types:
              SPECIFIC_CLASSES[attr_type] = cls
          type_fld = LLTDAttribute.fields_desc[0].copy()
          type_fld.default = attr_types[0]
          cls.fields_desc = [type_fld] + cls.fields_desc
          return cls
      return _register