### What changes were proposed in this pull request?
The class `KMeansSummary` in pyspark is not included in `clustering.py`'s `__all__` declaration. It isn't included in the docs as a result.
`InheritableThread` and `KMeansSummary` should be into corresponding RST files for documentation.
### Why are the changes needed?
It seems like an oversight to not include this as all similar "summary" classes are.
`InheritableThread` should also be documented.
### Does this PR introduce _any_ user-facing change?
I don't believe there are functional changes. It should make this public class appear in docs.
### How was this patch tested?
Existing tests / N/A.
Closes#29470 from srowen/KMeansSummary.
Lead-authored-by: Sean Owen <srowen@gmail.com>
Co-authored-by: HyukjinKwon <gurwls223@apache.org>
Signed-off-by: HyukjinKwon <gurwls223@apache.org>
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