code: def register_representer_class(self, representer_class):
          
          if representer_class in self.__rpr_classes.values():
              raise ValueError('The representer class "%s" has already been '
                               'registered.' % representer_class)
          self.__rpr_classes[representer_class.content_type] = representer_class
          if issubclass(representer_class, MappingResourceRepresenter):
              # Create and hold a mapping registry for the registered resource
              # representer class.
              mp_reg = representer_class.make_mapping_registry()
              self.__mp_regs[representer_class.content_type] = mp_reg
docs: Registers the given representer class with this registry, using
          its MIME content type as the key.