antd-vue 时间选择器设置mode=year无效

<a-date-picker 
    format="YYYY"
    mode="year"
    :value="year"
    :open="isopen"
    @openChange="openChange"
    @panelChange="panelChange"
/>    

openChange(status) {
    if (status) {
        this.isopen = true
    } else {
         this.isopen = false
    }
},
panelChange(value){
    this.year = value;
    this.isopen = false;
},