text: 
  import Vue from 'vue'
  function DataTransfer (data) {
    if (!(this instanceof DataTransfer)) {
      return new DataTransfer(data, null, null)
    }
  }
  
  DataTransfer.treeToArray = function (data, parent, level, expandedAll) {
    console.log(data);
    let tmp = []
    Array.from(data).forEach(function (record) {
      if (record._expanded === undefined) {
        Vue.set(record, '_expanded', expandedAll)
      }
      if (parent) {
        Vue.set(record, '_parent', parent)
      }
      let _level = 0
      if (level !== undefined && level !== null) {
        _level = level + 1
      }
      Vue.set(record, '_level', _level)
      tmp.push(record)
      if (record.children && record.children.length > 0) {
        let children = DataTransfer.treeToArray(record.children, record, _level, expandedAll)
        tmp = tmp.concat(children)
      }
    })
    return tmp
  }
  
  export default DataTransfer
  