typing.get_origin behaves differently between standard collections and typing collections

Bug report

typing.get_origin behaves differently between standard collections, and typing collections
more specifically

get_origin(dict) is None, while get_origin(Dict) is <class 'dict'>
the same holds for other collections as well

This is true from python3.9 where support for standard collections was added

to my understanding dict should be able to be a drop-in replacement for Dict, which is not true in case relying on get_origin

I suggest updating get_origin to return the relevant class for builtin collections as opposed to None which returns today

note, this might mean a breaking change, as pointed out here, but id does make Dict and dict behave more similarly

首先，针对报告中描述的 dict、Dict 以及其他集合类型对，复现 typing.get_origin 的行为。阅读现有的 get_origin 实现及其测试，然后查看关于破坏性变更风险的讨论。当预期行为达成一致，并且相关的集合类型情况得到一致覆盖时，即视为完成。