code: function(fields, visible) {
          if (!$.isArray(fields)) {
              fields = [fields];
          }
          var self = this;
          $.each(fields, function(index, field) {
              $.each(self.options.column, function(i, col) {
                  if (col.field === field) {
                      col.visible = visible;
                  }
              });
          });
          this.refresh();
      }
docs: 设置列显隐
  @param {String|Array} fields  列字段
  @param {Boolean}      visible 列字段
  @private