使用vue.js从element-ui导入树需要做什么才能使用sloped-slot？

import Vue from 'vue';
import ElementUI from 'element-ui';
import 'element-ui/lib/theme-chalk/index.css';

Vue.use(ElementUI);

import { Tree, SlopedSlot } from 'element-ui';

<template>
  <div>
    <el-tree :data="treeData">
      <span class="custom-tree-node" slot-scope="{ node, data }">
        <el-checkbox v-model="node.checked"></el-checkbox>
        <span>{{ data.label }}</span>
      </span>
    </el-tree>
  </div>
</template>

data() {
  return {
    treeData: [
      {
        label: 'Node 1',
        children: [
          {
            label: 'Child 1'
          },
          {
            label: 'Child 2'
          }
        ]
      },
      {
        label: 'Node 2'
      }
    ]
  };
}