code: def add(self, search):
          
          ms = self._clone()
          ms._searches.append(search)
          return ms
docs: Adds a new :class:`~elasticsearch_dsl.Search` object to the request::
  
              ms = MultiSearch(index='my-index')
              ms = ms.add(Search(doc_type=Category).filter('term', category='python'))
              ms = ms.add(Search(doc_type=Blog))