@Test
    public void testReturnTypes() {
        assertEquals("1", __.__(1).asString(Scope.local).next());
        assertArrayEquals(new String[]{"1", "2"}, __.inject(1, 2).asString(Scope.local).toList().toArray());
        assertArrayEquals(new String[]{}, ((List<?>) __.__(Collections.emptyList()).asString(Scope.local).next()).toArray());
        assertArrayEquals(new String[]{"1", "2", null}, ((List<?>) __.__(Arrays.asList(1, 2, null)).asString(Scope.local).next()).toArray());

        assertArrayEquals(new String[]{"1test", "2test"},
                __.__(Arrays.asList(1, 2)).asString(Scope.local).unfold().concat("test").toList().toArray());
    }
@author Yang Xia (http://github.com/xiazcy)
gremlin-core/src/test/java/org/apache/tinkerpop/gremlin/process/traversal/step/map/AsStringLocalStepTest.java