code: function() {
                  if (!that.model._provideSearchHelper) {
                      return null;
                  }
                  var prevPage = that.caculatePrevPage();
                  var qParams = mSearchUtils.copySearchParams(that.model._provideSearchHelper().params, true);
                  qParams.start = prevPage.start;
                  return mSearchUtils.generateSearchHref(qParams);
              }
docs: $NON-NLS-0$