@Test
    public void testReturnTypes() {
        assertEquals(Integer.valueOf(4), __.__("test").length().next());
        assertArrayEquals(new Integer[]{5, 4, null, 0}, __.inject("hello", "test", null, "").length().toList().toArray());
    }
@author Yang Xia (http://github.com/xiazcy)
gremlin-core/src/test/java/org/apache/tinkerpop/gremlin/process/traversal/step/map/LengthGlobalStepTest.java