@Test
    public void testReturnTypes() {
        assertEquals("HELLO", __.__("hello").toUpper(Scope.local).next());
        assertArrayEquals(new String[]{"TEST"}, ((List<?>) __.__(Collections.singletonList("test")).toUpper(Scope.local).next()).toArray());
        assertArrayEquals(new String[]{"TEST"}, ((List<?>) __.__(new HashSet<>(Collections.singletonList("test"))).toUpper(Scope.local).next()).toArray());
        assertArrayEquals(new String[]{"HELLO", "TEST", "NO.123", null, ""},
                ((List<?>) __.__(Arrays.asList("hElLo", "test", "no.123", null, "")).toUpper(Scope.local).next()).toArray());
    }
@author Yang Xia (http://github.com/xiazcy)
gremlin-core/src/test/java/org/apache/tinkerpop/gremlin/process/traversal/step/map/ToUpperLocalStepTest.java