presto-main/src/main/java/io/prestosql/sql/gen/LambdaExpressionExtractor.java/LambdaExpressionExtractor/visitInputReference
class LambdaExpressionExtractor:        @Override
        public Void visitInputReference(InputReferenceExpression node, Context context)
        {
            // TODO: change such that CallExpressions only capture the inputs they actually depend on
            return null;
        }