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Many subclasses (Reviewer Review)
A class with many subclasses is an important class in the model. This review is not indicating an error, it just highlights the class so that it can be reviewed in more detail.
Consequences
Classes which have many subclasses need to ensure that they truly are the subset of commonality between the subclasses, and not a convenient union of all subclass functionality.
Strategy
Check the class, once you are happy with it ignore this review item.