let bam_of_input_exn u =     let open Input in     match u with     | Fastq _ -> failwith "Can't pass Input.t Fastq to bam_of_input_exn"     | Bam {bam_sample_name; path; how; sorting; reference_build} ->       let f = Bfx.input_url path in       Bfx.bam ~sample_name:bam_sample_name ?sorting ~reference_build f