我有一个带有3个字段的配置json，第3个字段是根据前2个字段中的数据计算出来的字段。这里的关键是我在他们的主要名字中有点（.）。e、 g.“something.someone”当我尝试渲染表单时，会出现一个显示未定义的错误。我的配置文件：

{
"fieldGroupClassName": "row",
"fieldGroup": [
{
            "className": "col-2",
            "key": "remarks_backflow.bed",
            "type": "input",
            "templateOptions": {
              "type": "number",
              "label": "Bed",
              "placeholder": "",
              "required": true
            }
          },
{
            "className": "col-2",
            "key": "remarks_backflow.gas",
            "type": "input",
            "templateOptions": {
              "type": "number",
              "label": "Gas",
              "placeholder": "",
              "required": true
            }
          },
{
            "className": "col-2",
            "key": "remarks_backflow.diff",
            "type": "input",
            "templateOptions": {
              "type": "number",
              "label": "Difference",
              "placeholder": "",
              "required": true
            },
            "expressionProperties": {
              "model['remarks_backflow.diff']":"model['remarks_backflow.bed'] - model['remarks_backflow.gas']"
            }
          },
]
}

错误是：formbuildercomponent.html:24错误类型错误：[formly error][表达式“model['pushin_temperature.kille_id']”无法设置未定义的属性“kille_id']”

提前谢谢！