@Test
    public void shouldPutCollectionInSet() {
        final Map<String,Set<Object>> multi = new HashMap<>();
        final Set<Object> expected = new HashSet<Object>() {{
            add(1);
            add(2);
        }};
        MultiMap.putAll(multi, "here", expected);
        assertEquals(expected, multi.get("here"));
    }
@author Stephen Mallette (http://stephen.genoprime.com)
gremlin-core/src/test/java/org/apache/tinkerpop/gremlin/util/MultiMapTest.java