@Test
    public void shouldHaveValidLegalEnumOrdering() {
        assertTrue(GraphFilter.Legal.YES.compareTo(GraphFilter.Legal.YES) == 0);
        assertTrue(GraphFilter.Legal.YES.compareTo(GraphFilter.Legal.NO) < 0);
        assertTrue(GraphFilter.Legal.YES.compareTo(GraphFilter.Legal.MAYBE) < 0);
        assertTrue(GraphFilter.Legal.MAYBE.compareTo(GraphFilter.Legal.NO) < 0);
    }
@author Marko A. Rodriguez (http://markorodriguez.com)
gremlin-core/src/test/java/org/apache/tinkerpop/gremlin/process/computer/GraphFilterTest.java