code: def add_file_argument(self, *args, mode='r', buffering=1,
                            filetype_options=None, **kwargs):
          
          type_ = supplement.SafeFileType(mode=mode, bufsize=buffering,
                                          **filetype_options or {})
          return self.add_argument(*args, type=type_, **kwargs)
docs: Add a tab-completion safe FileType argument.  This argument
          differs from a normal argparse.FileType based argument in that the
          value is a factory function that returns a file handle instead of
          providing an already open file handle.  There are various reasons
          why this is a better approach but it is also required to avoid
          erroneous creation of files with shellish tab completion.