code: def simple_filter(self, key, value):
          "Search keys whose values match with the searched values"
          searched = {key: value}
          return set([k for k, v in self.data.items() if
                      intersect(searched, v) == searched]f simple_filter(self, key, value):
          "Search keys whose values match with the searched values"
          searched = {key: value}
          return set([k for k, v in self.data.items() if
                      intersect(searched, v) == searched])
docs: Search keys whose values match with the searched values