output: #fixed code
                                private Set<T> aggregateSet() {
      if (areAllInitial(changeNotifiers)) {
        return ChangeNotifiers.initialEmptyDataInstance();
      }
  
      ImmutableSet.Builder<T> records = ImmutableSet.builder();
      for (final ChangeNotifier<T> changeNotifier : changeNotifiers) {
        records.addAll(changeNotifier.current());
      }
      return records.build();
    }
input: #vulnerable code 
                                private Set<T> aggregateSet() {
      ImmutableSet.Builder<T> records = ImmutableSet.builder();
      for (final ChangeNotifier<T> changeNotifier : changeNotifiers) {
        records.addAll(changeNotifier.current());
      }
      return records.build();
    } 
                              #location 1 
                              #vulnerability type CHECKERS_IMMUTABLE_CAST