text: from wagtail.wagtailsearch.backends import get_search_backend
  
  
  class SearchableQuerySetMixin(object):
      def search(self, query_string, fields=None,
                 operator=None, order_by_relevance=True, backend='default'):
          """
          This runs a search query on all the items in the QuerySet
          """
          search_backend = get_search_backend(backend)
          return search_backend.search(query_string, self, fields=fields,
                                       operator=operator, order_by_relevance=order_by_relevance)
  