guava/src/com/google/common/collect/AbstractMapBasedMultimap.java
Collection<V> wrapCollection(@Nullable K key, Collection<V> collection) {
    return new WrappedCollection(key, collection, null);
  }
Collection<V> wrapCollection(@Nullable K key, Collection<V> collection) {
    return new WrappedCollection(key, collection, null);
  }
Collection < V > wrapCollection ( @ Nullable K key , Collection < V > collection ) { return new WrappedCollection ( key , collection , null ) ; }
Generates a decorated collection that remains consistent with the values in the multimap for
the provided key. Changes to the multimap may alter the returned collection, and vice versa.
Generates a decorated collection that remains consistent with the values in the multimap for the provided key . Changes to the multimap may alter the returned collection and vice versa .