code: function(options) {
          var borderTopRule = classRule(classNameConst.BORDER_TOP).bg(options.border);
          var borderBottomRule = classComposeRule(' .', [
              classNameConst.NO_SCROLL_X,
              classNameConst.BORDER_BOTTOM
          ]).bg(options.border);
          var rules = [
              borderTopRule,
              borderBottomRule
          ];
          var borderLeftRule, borderRightRule;
  
          if (options.showVerticalBorder) {
              borderLeftRule = classRule(classNameConst.BORDER_LEFT).bg(options.border);
              borderRightRule = classComposeRule(' .', [
                  classNameConst.NO_SCROLL_Y,
                  classNameConst.BORDER_RIGHT
              ]).bg(options.border);
  
              rules = rules.concat([borderLeftRule, borderRightRule]);
          }
  
          return builder.buildAll(rules);
      }
docs: Generates a css string for grid outline.
  @param {Object} options - options
  @returns {String}