* clear()} are called on the filtered multiset, only elements that satisfy the filter will be
   * removed from the underlying multiset.
   *
   * <p>The returned multiset isn't threadsafe or serializable, even if {@code unfiltered} is.
   *
   * <p>Many of the filtered multiset's methods, such as {@code size()}, iterate across every

   * such as {@code removeAll()} and {@code clear()} are called on the filtered set, only elements
   * that satisfy the filter will be removed from the underlying set.
   *
   * <p>The returned set isn't threadsafe or serializable, even if {@code unfiltered} is.
   *
   * <p>Many of the filtered set's methods, such as {@code size()}, iterate across every element in

   *
   * <p>The multimap is serializable if {@code map}, {@code factory}, the collections generated by
   * {@code factory}, and the multimap contents are all serializable.
   *
   * <p>The multimap is not threadsafe when any concurrent operations update the multimap, even if
   * {@code map} and the instances generated by {@code factory} are. Concurrent read operations will

   * or its views, only mappings whose keys satisfy the filter will be removed from the underlying
   * map.
   *
   * <p>The returned map isn't threadsafe or serializable, even if {@code unfiltered} is.
   *
   * <p>Many of the filtered map's methods, such as {@code size()}, iterate across every key/value