public Set<ValidationEvent> determineIntroducedEvents() {
            Set<ValidationEvent> events = new TreeSet<>(getNewModelEvents());
            events.removeAll(getOldModelEvents());
            return events;
        }
Gets the validation events that were introduced by whatever changes
were made to the new model.

@return Returns the validation events introduced by the new model.
smithy-diff/src/main/java/software/amazon/smithy/diff/ModelDiff.java