let to_json t: Yojson.Basic.json =       let {name;            filter_reads_with_n_cigar;            filter_mismatching_base_and_quals;            filter_bases_not_stored;            parameters} = t in       `Assoc [         "name", `String name;         "filter_reads_with_N_cigar", `Bool filter_reads_with_n_cigar;         "filter_mismatching_base_and_quals", `Bool filter_mismatching_base_and_quals;         "filter_bases_not_stored", `Bool filter_bases_not_stored;         "parameters",         `Assoc (List.map parameters ~f:(fun (a, b) -> a, `String b));       ]