code: def extend(self, *blues, memo=None):
          
          from .utils.blue import BlueDispatcher as Blue
          return Blue().extend(*blues, memo=memo).register(self, memo=memo)
docs: Extends Dispatcher calling each deferred operation of given Blueprints.
  
          :param blues:
              Blueprints or Dispatchers to extend deferred operations.
          :type blues: Blueprint | schedula.dispatcher.Dispatcher
  
          :param memo:
              A dictionary to cache Blueprints and Dispatchers.
          :type memo: dict[T,schedula.utils.blue.Blueprint|Dispatcher]
  
          :return:
              Self.
          :rtype: Dispatcher
  
          **--------------------------------------------------------------------**
  
          **Example**:
  
          .. dispatcher:: dsp
             :opt: graph_attr={'ratio': '1'}
             :code:
  
              >>> import schedula as sh
              >>> dsp = sh.Dispatcher()
              >>> dsp.add_func(callable, ['is_callable'])
              'callable'
              >>> blue = sh.BlueDispatcher().add_func(len, ['length'])
              >>> dsp = sh.Dispatcher().extend(dsp, blue)