argparse: undocumented `nargs` constants `ONE_OR_MORE`, `OPTIONAL`, `PARSER`, `REMAINDER`, `ZERO_OR_MORE`, `SUPPRESS`

Concerning the possible values of the nargs parameter of add_argument().

The following values are already described in the documentation, so only a mention of the constants is needed:

• OPTIONAL = ?
• ZERO_OR_MORE = *
• ONE_OR_MORE = +

The following constants and their values do not seem to be documented anywhere:

• PARSER
• REMAINDER

SUPPRESS constant was documented for help parameter in https://github.com/python/cpython/issues/53595, but not for nargs.

先查看 argparse 中 ArgumentParser.add_argument() 及其 nargs 参数的文档，然后检查现有的 help 参数文档如何描述 SUPPRESS。为 issue 中列出的 nargs 常量编写文档，包括 OPTIONAL、ZERO_OR_MORE 和 ONE_OR_MORE 的值，以及缺失的 PARSER 和 REMAINDER 描述；当所有列出的常量都已覆盖时完成。