private ImmutableList<ParseTree> parseImportSpecifierSet() {
    ImmutableList.Builder<ParseTree> elements;
    elements = ImmutableList.builder();
    eat(TokenType.OPEN_CURLY);
    while (peekIdOrKeyword()) {
      elements.add(parseImportSpecifier());
      if (!peek(TokenType.CLOSE_CURLY)) {
        eat(TokenType.COMMA);
      }
    }
    eat(TokenType.CLOSE_CURLY);
    return elements.build();
  }
private ImmutableList < ParseTree > parseImportSpecifierSet ( ) { ImmutableList . Builder < ParseTree > elements ; elements = ImmutableList . builder ( ) ; eat ( TokenType . OPEN_CURLY ) ; while ( peekIdOrKeyword ( ) ) { elements . add ( parseImportSpecifier ( ) ) ; if ( ! peek ( TokenType . CLOSE_CURLY ) ) { eat ( TokenType . COMMA ) ; } } eat ( TokenType . CLOSE_CURLY ) ; return elements . build ( ) ; }
ImportSpecifierSet ::= '{' (ImportSpecifier (',' ImportSpecifier)* (,)? )?  '}'