presto-parser/src/main/java/io/prestosql/sql/tree/DefaultTraversalVisitor.java/DefaultTraversalVisitor/visitIfExpression
class DefaultTraversalVisitor:    @Override
    protected R visitIfExpression(IfExpression node, C context)
    {
        process(node.getCondition(), context);
        process(node.getTrueValue(), context);
        if (node.getFalseValue().isPresent()) {
            process(node.getFalseValue().get(), context);
        }

        return null;
    }