private @Nullable String parseIdentifier(final IElementType elementType) {
    final SyntaxTreeBuilder.Marker idMarker = myBuilder.mark();
    if (myBuilder.getTokenType() == PyTokenTypes.IDENTIFIER) {
      String id_text = myBuilder.getTokenText();
      myBuilder.advanceLexer();
      idMarker.done(elementType);
      return id_text;
    }
    else {
      myBuilder.error(PyParsingBundle.message("PARSE.expected.identifier"));
      idMarker.drop();
    }
    return null;
  }
private @Nullable String parseIdentifier(final IElementType elementType)