@Test(expected = IllegalArgumentException.class)
    public void shouldThrowWithIncomingArrayList() {
        __.__(Arrays.asList(" a ", " b ", " c" )).lTrim().next();
    }
@author Yang Xia (http://github.com/xiazcy)
gremlin-core/src/test/java/org/apache/tinkerpop/gremlin/process/traversal/step/map/LTrimGlobalStepTest.java