@Test
    public void shouldGetMultipleUsingTraverserOverload() {
        final Parameters parameters = new Parameters();
        parameters.set(null, "a", "axe", "a", "ant", "b", "bat", "b", "ball", "c", "cat");

        final Map<Object,List<Object>> params = parameters.getRaw();
        assertEquals(3, params.size());
        assertEquals(Arrays.asList("axe", "ant"), parameters.get(mock(Traverser.Admin.class), "a", () -> "x"));
        assertEquals(Arrays.asList("bat", "ball"), parameters.get(mock(Traverser.Admin.class), "b", () -> "x"));
        assertEquals(Collections.singletonList("cat"), parameters.get(mock(Traverser.Admin.class), "c", () -> "x"));
        assertEquals(Collections.singletonList("zebra"), parameters.get(mock(Traverser.Admin.class), "z", () -> "zebra"));
    }
@author Stephen Mallette (http://stephen.genoprime.com)
gremlin-core/src/test/java/org/apache/tinkerpop/gremlin/process/traversal/step/util/ParametersTest.java