public static <K, V> boolean putAll(final Map<K, Set<V>> map, final K key, final Collection<V> values) {
        return getMapSet(map, key).addAll(values);
    }
A number of static methods to interact with a multi map, i.e. a map that maps keys to sets of values.

@author Matthias Broecheler (me@matthiasb.com)
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/util/MultiMap.java