[python] Fix Circular imports on inherited discriminators.

[fa0311]

Same as #17882, but passed type analysis and added a test

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@cbornet (2017/09) @tomplus (2018/10) @krjakbrjak (2023/02) @fa0311 (2023/10) @multani (2023/10)

[wing328]

thanks for the PR.

minor suggestions:

1. use the following to avoid the empty line break

{{#hasChildren}}
{{#discriminator}}
...
{{/discriminator}}
{{/hasChildren}}

2. for line 22 (empty line), move it between line 20 and 21 so that it will only be included when both hasChilden and discriminator are non-emtpy (or true)

[fa0311]

This issue has been fixed.

[wing328]

lgtm. thanks for the fix 👍