code: function serializeAttrs(attributes, opts) {
      if (!attributes) {
          return;
      }
  
      let output = '';
      let value;
      Object.keys(attributes).forEach(key => {
          value = attributes[key];
          if (output) {
              output += ' ';
          }
  
          let isBoolAttr = value && typeof value === 'boolean';
          if (isBoolAttr) {
              output += key;
          }
          else {
              output += key + '="' + (opts.decodeEntities ? entities.encodeXML(value) : value) + '"';
          }
      });
  
      return output;
  }
docs: Serialize tag attributes info
  
  @inner
  @param {Object} attributes tag attributes info
  @param {Object} opts the serialize options
  @return {string}