presto-parser/src/main/java/io/prestosql/sql/tree/DefaultTraversalVisitor.java/DefaultTraversalVisitor/visitWindow
class DefaultTraversalVisitor:    @Override
    public R visitWindow(Window node, C context)
    {
        for (Expression expression : node.getPartitionBy()) {
            process(expression, context);
        }

        if (node.getOrderBy().isPresent()) {
            process(node.getOrderBy().get(), context);
        }

        if (node.getFrame().isPresent()) {
            process(node.getFrame().get(), context);
        }

        return null;
    }