return false;
      }
    }
    return true;
  }

  private static <E extends @Nullable Object> ObjectCountHashMap<E> counts(
      Collection<E> collection) {
    ObjectCountHashMap<E> map = new ObjectCountHashMap<>();
    for (E e : collection) {
      map.put(e, map.get(e) + 1);
    }
    return map;
  }