@Test
    public void shouldGetEmptyIfKeyNotPresent() {
        final Map<String,Set<Object>> multi = new HashMap<>();
        MultiMap.put(multi, "here", 1);
        MultiMap.put(multi, "there", 3);

        assertEquals(Collections.emptySet(), MultiMap.get(multi, "not-here"));
    }
@author Stephen Mallette (http://stephen.genoprime.com)
gremlin-core/src/test/java/org/apache/tinkerpop/gremlin/util/MultiMapTest.java