"--format", Arg.String set_format, "format Set format";
"-v", Arg.Unit set_verbose_flag, " Enable debugging messages";
"--verbose", Arg.Unit set_verbose_flag, " Enable debugging messages";
"--format", Arg.String set_format, "format Set format";
"-v", Arg.Unit set_verbose_flag, " Enable debugging messages";
"--verbose", Arg.Unit set_verbose_flag, " Enable debugging messages";