code: def get_querydict(self):
          
          if self.method:
              querydict =  getattr(self.request, self.method.upper())
          else:
              querydict =  getattr(self.request, 'POST'.upper())
          # copy make querydict mutable
  
          query_dict =  dict(querydict.items())
          return query_dict
docs: 这个函数跟 self.method有关
          self.method 暂时没用, querydict都是POST的