How to use the xe-utils.sum function in xe-utils

columns.map((column, columnIndex) => {
          if (columnIndex === 0) {
            return `合计 (${XEUtils.sum(data, 'num')}人)`
          }
          switch (column.property) {
            case 'level':
              return `总共 ${Math.floor(XEUtils.sum(data, 'level'))}`
            case 'age':
              return `平均年龄 ${parseInt(XEUtils.mean(data, 'age'))}`
            case 'rate':
              return `总分 ${XEUtils.sum(data, 'rate')}`
          }
          return '-'
        })
      ]

handleSummary  (children) {
      return {
        num: XEUtils.sum(children, 'num'),
        level: Math.floor(XEUtils.sum(children, 'level')),
        age: parseInt(XEUtils.mean(children, 'age')),
        rate: XEUtils.sum(children, 'rate')
      }
    },
    getGroupSummary (data) {

columns.forEach((column, index) => {
          if (index === 0) {
            sums[index] = this.sumText || (this.$t ? this.$t('el.table.sumText') : '合计')
            return
          }
          sums[index] = data.some(item => isNaN(Number(item[column.property]))) ? '' : XEUtils.sum(data, column.property)
        })
      }

columns.map((column, columnIndex) => {
          if (columnIndex === 0) {
            return '和值'
          }
          if (['age', 'rate'].includes(column.property)) {
            return XEUtils.sum(data, column.property)
          }
          return null
        })
      ]

handleSummary  (children) {
      return {
        num: XEUtils.sum(children, 'num'),
        level: Math.floor(XEUtils.sum(children, 'level')),
        age: parseInt(XEUtils.mean(children, 'age')),
        rate: XEUtils.sum(children, 'rate')
      }
    },
    getGroupSummary (data) {

columns.map((column, columnIndex) => {
          if (columnIndex === 0) {
            return `合计 (${XEUtils.sum(data, 'num')}人)`
          }
          switch (column.property) {
            case 'level':
              return `总共 ${Math.floor(XEUtils.sum(data, 'level'))}`
            case 'age':
              return `平均年龄 ${parseInt(XEUtils.mean(data, 'age'))}`
            case 'rate':
              return `总分 ${XEUtils.sum(data, 'rate')}`
          }
          return '-'
        })
      ]

columns.map((column, columnIndex) => {
          if (columnIndex === 0) {
            return `合计 (${XEUtils.sum(data, 'num')}人)`
          }
          switch (column.property) {
            case 'level':
              return `总共 ${Math.floor(XEUtils.sum(data, 'level'))}`
            case 'age':
              return `平均年龄 ${parseInt(XEUtils.mean(data, 'age'))}`
            case 'rate':
              return `总分 ${XEUtils.sum(data, 'rate')}`
          }
          return '-'
        })
      ]

handleSummary  (children) {
      return {
        num: XEUtils.sum(children, 'num'),
        level: Math.floor(XEUtils.sum(children, 'level')),
        age: parseInt(XEUtils.mean(children, 'age')),
        rate: XEUtils.sum(children, 'rate')
      }
    },
    getGroupSummary (data) {

columns.map((column, columnIndex) => {
          if (columnIndex === 0) {
            return '和值'
          }
          if (['age', 'rate'].includes(column.property)) {
            return XEUtils.sum(data, column.property)
          }
          return null
        }),
        columns.map((column, columnIndex) => {