code: def run_cmd_if_file_missing(cmd, fname, out=os.path.devnull, err=os.path.devnull):
      
  
      if fname is None or not os.path.exists(fname):
          run_cmd(cmd, out, err)
          return True
      else:
          return False
docs: Runs an external command if file is absent.
  
      :param list cmd: Command to run.
      :param str fname: Path to the file, which existence is being checked.
      :param str out: Output file
      :param str err: Error file
      :return: True if cmd was executed, False otherwise
      :rtype: boolean