code: def extend(self, definitions):
          
          for name, definition in dict(definitions).items():
              self.add(name, definition)
docs: Add several definitions at once. Existing definitions are
          replaced silently.
  
          :param definitions: The names and definitions.
          :type definitions: a :term:`mapping` or an :term:`iterable` with
                             two-value :class:`tuple` s