docs: def check_infile(filename):
      """Check text file exisitense.
  
      Argument:
  
          filename: text file of bulk updating
      """
      if os.path.isfile(filename):
          domain = os.path.basename(filename).split('.txt')[0]
          return domain
      else:
          sys.stderr.write("ERROR: %s : No such file\n" % filename)
          sys.exit(1)