code: def check_bed_file(fname):
      
      if not os.path.exists(fname):
          logger.error("Inputfile %s does not exist!", fname)
          sys.exit(1)
  
      for i, line in enumerate(open(fname)):
          if line.startswith("#") or line.startswith("track") or line.startswith("browser"):
              # comment or BED specific stuff
              pass
          else:
              vals = line.strip().split("\t")
              if len(vals) < 3:
                  logger.error("Expecting tab-seperated values (chromosome<tab>start<tab>end) on line %s of file %s", i + 1, fname)
                  sys.exit(1)
              try:
                  start, end = int(vals[1]), int(vals[2])
              except ValueError:
                  logger.error("No valid integer coordinates on line %s of file %s", i + 1, fname)
                  sys.exit(1)
              if len(vals) > 3:
                  try:
                      float(vals[3])
                  except ValueError:
                      pass
docs: Check if the inputfile is a valid bed-file