presto-parser/src/main/java/io/prestosql/sql/parser/AstBuilder.java/AstBuilder/visitGroupBy
class AstBuilder:    @Override
    public Node visitGroupBy(SqlBaseParser.GroupByContext context)
    {
        return new GroupBy(getLocation(context), isDistinct(context.setQuantifier()), visit(context.groupingElement(), GroupingElement.class));
    }