code: def _to_url(self):
          
          url = self._target_url
  
          params = collections.defaultdict(list, copy.deepcopy(self._filters))
          if self._order_by is not None:
              params['sort'] = self._order_by
          for k, vl in self._extra.items():
              params[k] += vl
  
          if params:
              url += "?" + urllib.parse.urlencode(params, doseq=True)
  
          return url
docs: Serialises this query into a request-able URL including parameters