presto-parser/src/main/java/io/prestosql/sql/tree/ExpressionTreeRewriter.java/ExpressionTreeRewriter/visitAtTimeZone
class ExpressionTreeRewriter:        @Override
        protected Expression visitAtTimeZone(AtTimeZone node, Context<C> context)
        {
            if (!context.isDefaultRewrite()) {
                Expression result = rewriter.rewriteAtTimeZone(node, context.get(), ExpressionTreeRewriter.this);
                if (result != null) {
                    return result;
                }
            }

            Expression value = rewrite(node.getValue(), context.get());
            Expression timeZone = rewrite(node.getTimeZone(), context.get());

            if (value != node.getValue() || timeZone != node.getTimeZone()) {
                return new AtTimeZone(value, timeZone);
            }

            return node;
        }