presto-main/src/main/java/io/prestosql/sql/planner/optimizations/ExpressionEquivalence.java/ExpressionEquivalence/swapPair
class ExpressionEquivalence:    private static <T> List<T> swapPair(List<T> pair)
    {
        requireNonNull(pair, "pair is null");
        checkArgument(pair.size() == 2, "Expected pair to have two elements");
        return ImmutableList.of(pair.get(1), pair.get(0));
    }