#尝试实现简单的插件功能
$ python main.py -h
usage: main.py [-h] [--enable PLUGINS]
optional arguments:
-h, --help show this help message and exit
--enable PLUGINS enable some plugins (default: [])
默认输出：
$ python main.py
Default: test plugin.
启用插件 foo:
$ python main.py --enable foo
Default: test plugin.
Plugin foo: test plugin.
启用插件 foo, bar:
$ python main.py --enable foo --enable bar
Default: test plugin.
Plugin bar: test plugin.
Plugin foo: test plugin.