code: def file_plus_index(fname):
      
      exts = {".vcf": ".idx", ".bam": ".bai", ".vcf.gz": ".tbi", ".bed.gz": ".tbi",
              ".fq.gz": ".gbi"}
      ext = splitext_plus(fname)[-1]
      if ext in exts:
          return [fname, fname + exts[ext]]
      else:
          return [fname]
docs: Convert a file name into the file plus required indexes.