let read_2_file_node (fq : fastq_reads workflow_node) =     Option.map fq#product#r2 ~f:(fun product ->         workflow_node product           ~name:(sprintf "READ2 of %s-%s"                    fq#product#sample_name                    fq#product#fragment_id_forced)           ~equivalence:`None           ~edges:[depends_on fq]       )