Nionutils

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- Add Platform utility classes.

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- Performance improvements to filtered list model.
- Add pop_item to ListModel and item_count to FilteredListModel.

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- Add BoolToStringConverter.
- Allow override of get/set property value in PropertyChangedPropertyModel for more flexibility.
- Change binding to hold reference to source.
- Make point/size/rect classes hashable.
- Add equality operator to color; make it hashable.
- Clean up ticker class, make it immutable and hashable.
- Add ObservedListModel to create a list model from a collection on an observable.
- Drop Python 3.9, 3.10. Add Python 3.13.

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- Add ability to filter audit reports by top-level audit id.
- Add replace_stream method and stream_list property to CombineLatestStream.
- Add FollowStream utility class.

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- OptionalStream now returns the proper value.
- Improvements to ValueChangeStreamReactor (still experimental).

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- Minor updates for Python 3.12 compatibility.
- Avoid using utcnow and utcfromtimestamp (both deprecated).