This class is the base of the viewproviders of annotation-type
objects like dimensions (linear, radial, angular), labels,
and texts.
The basic properties of `ViewProviderDraftAnnotation`
are set up by a method `set_properties`, which can be called
in the derived classes.
In the general proxy object `DraftAnnotation` we implement
the `onDocumentRestored` method in order to add the missing
view property `AnnotationStyle` to older objects.
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