question: public Collection < AISValidationFailure > failures ( ) { return Collections . unmodifiableCollection ( failureList ) ; }
target:  Gets all failures, if there were any. The collection will be unmodifiable and immutable; if it is not empty, subsequent invocations of this method may all return same collection instance, but only as long as no additional failures are reported. If new failures are reported, they and the previous will be in a new collection instance.