code: def get_key_from_cmdline(parser, args):
      
      if args.keyfiles:
          signing_key = open(args.keyfiles[0], 'rb').read()
          bits = get_keysize(signing_key)
          if bits == 2048:
              signing_algorithm = 'sha1'
          elif bits == 4096:
              signing_algorithm = 'sha384'
          else:
              parser.error("Unsupported key size {} from key {}".format(bits, args.keyfiles[0]))
  
          print("Using {} to sign using algorithm {!s}".format(args.keyfiles[0], signing_algorithm))
      else:
          signing_key = None
          signing_algorithm = None
  
      return signing_key, signing_algorithm
docs: Return the signing key and signing algoritm from the commandline.