code: function(options) {
          var contentAreaRule = classRule(classNameConst.SUMMARY_AREA)
              .bg(options.background)
              .border(options.border);
          var bodyAreaRule = classComposeRule(' .', [
              classNameConst.HAS_SUMMARY_TOP,
              classNameConst.BODY_AREA
          ]).border(options.border);
  
          return builder.buildAll([
              contentAreaRule,
              bodyAreaRule
          ]);
      }
docs: Generates a css string for summary area.
  @param {Object} options - options
  @returns {String}