code: function(results, filename, options) {
          "use strict";
          if (results.messages.length > 0 || !options.quiet) {
              this.json.push({
                  filename: filename,
                  messages: results.messages,
                  stats: results.stats
              });
          }
          return "";
      }
docs: Given CSS Lint results for a file, return output for this format.
  @param results {Object} with error and warning messages
  @param filename {String} relative file path (Unused)
  @return {String} output for results