When parsing enums derived from `enum.Enum`, non-canonical values are ignored

My package does not use pybind11 hacky enums, but instead derives enums from enum.Enum using a popular helper macro.

However, in that case the generated stub does not contain some values, the ones that are considered non-canonical (as defined in this comment). These are zero values (maybe just in enum.Flag) and repeated/alias values.

I haven't looked at the implementation, but the issue is probably related to this: https://github.com/python/cpython/issues/109633. If I'm correct, the issue can probable be fixed by iterating over the __members__ of the enum class.

Example of what I mean:

>>> list(iter(InputMode))
[<InputMode.UNICODE: 1>,
 <InputMode.GS1: 2>,
 <InputMode.ESCAPE: 8>,
 <InputMode.GS1PARENS: 16>,
 <InputMode.GS1NOCHECK: 32>,
 <InputMode.HEIGHTPERROW: 64>,
 <InputMode.FAST: 128>,
 <InputMode.EXTRA_ESCAPE: 256>]

>>> InputMode.__members__
mappingproxy({'DATA': <InputMode.DATA: 0>,
              'UNICODE': <InputMode.UNICODE: 1>,
              'GS1': <InputMode.GS1: 2>,
              'ESCAPE': <InputMode.ESCAPE: 8>,
              'GS1PARENS': <InputMode.GS1PARENS: 16>,
              'GS1NOCHECK': <InputMode.GS1NOCHECK: 32>,
              'HEIGHTPERROW': <InputMode.HEIGHTPERROW: 64>,
              'FAST': <InputMode.FAST: 128>,
              'EXTRA_ESCAPE': <InputMode.EXTRA_ESCAPE: 256>})

As you can see, with iter(), the DATA value is missing.

Start by locating the enum parsing or stub-generation entry point and compare its current iteration with Python enum.Enum.members. Reproduce the example with a zero-valued and repeated enum member, then add a regression test covering non-canonical values; done means the generated stub includes DATA and other members present in members.