code: function(){
                  /*
                   * element_name
                   *   : IDENT
                   *   ;
                   */
  
                  var tokenStream = this._tokenStream,
                      token;
  
                  if (tokenStream.match(Tokens.IDENT)){
                      token = tokenStream.token();
                      return new SelectorSubPart(token.value, "elementName", token.startLine, token.startCol);
  
                  } else {
                      return null;
                  }
              }
docs: CSS3 Selectors