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))

def add(self, search):
        """
        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))
        """
        ms = self._clone()
        ms._searches.append(search)
        return ms