docs: def get_pid_from_request(cls, changelist, request):
          """Gets parent ID from query string.
  
          :param changelist:
          :param request:
          :return:
          """
          val = request.GET.get(cls.PARENT_ID_QS_PARAM, False)
          pid = val or None
  
          try:
              del changelist.params[cls.PARENT_ID_QS_PARAM]
  
          except KeyError:
              pass
  
          return pid