docs: @SuppressWarnings({"unchecked", "SuspiciousMethodCalls"})
    private void makeGenericKeyCache(CoreLabel c) {
      genericAnnotationKeys = new HashSet<Class<? extends GenericAnnotation<?>>>();
      for (Class<?> key : c.keySet()) {
        if (CoreLabel.genericValues.containsKey(key)) {
          Class<? extends GenericAnnotation<?>> genKey = (Class<? extends GenericAnnotation<?>>) key;
          genericAnnotationKeys.add(genKey);
        }
      }
    }