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