vxe-table 3.6.9 导出树形表格序号问题：type="seq" 导出后显示为 -1 的解决方法

<p>```html
<template></p>
  <div>
    <vxe-table ref="treeTable" :data="dataList" :columns="columns"></vxe-table>
    <button @click="exportToExcel">导出 Excel</button>
  </div>
</template>
<script>
import XLSX from "xlsx";
import VXEtable from "vxe-table";
import "vxe-table/lib/style.css";

export default {
  data() {
    return {
      dataList: [
        { id: 1, name: "节点1", children: [{ id: 11, name: "子节点1" }] },
        { id: 2, name: "节点2", children: [{ id: 21, name: "子节点2" }] },
      ],
      columns: [
        { field: "id", title: "序号", type: "seq" },
        { field: "name", title: "名称" },
      ],
    };
  },
  methods: {
    exportToExcel() {
      const tableData = this.$refs.treeTable.getTableData();
      const sheet = XLSX.utils.json_to_sheet(tableData);
      const workbook = XLSX.utils.book_new();
      XLSX.utils.book_append_sheet(workbook, sheet, "Sheet1");
      XLSX.writeFile(workbook, "export.xlsx");
    },
  },
  mounted() {
    VXEtable.install(this.Vue);
    this.Vue.use(VXEtable);
  },
};
</script>
<p>```</p>
<p>在以上代码中，使用<code>vxe-table</code>的<code>getTableData</code>方法获取表格数据，然后使用<code>xlsx</code>库将数据转换为Excel文件并下载。请确保已安装<code>vxe-table</code>和<code>xlsx</code>库，并且在<code>mounted</code>钩子函数中正确引入和安装<code>vxe-table</code>库。</p>