code: def get_easyui_context(self, **kwargs):
          
          context = {}
          queryset = self.get_queryset()
          limit_queryset =  self.get_limit_queryset()
          data = model_serialize(limit_queryset, self.extra_fields, self.remove_fields)
          count = queryset.count()
          # datagrid 返回的数据中，total是总的行数，rows是查询到的结果集
          context.update(rows=data)
          context.update(total=count)
          return context
docs: 初始化一个空的context