computed: {
  showStart: function () {
      return function (item) {
          var contentType = item.contentType
          if (contentType != null && contentType.trim() != '') {
              var contentTypeList = item.contentType.split(',')
              for (var i of contentTypeList) {
                  if (i == 'z') {
                      return true
                  }
              }
          }
          return false
      }
  }
}