presto-main/src/main/java/io/prestosql/sql/planner/NullabilityAnalyzer.java/NullabilityAnalyzer/visitSubscriptExpression
class NullabilityAnalyzer:        @Override
        protected Void visitSubscriptExpression(SubscriptExpression node, AtomicBoolean result)
        {
            result.set(true);
            return null;
        }