public static L3ModificationInstruction copyTtlIn() {
        return new ModTtlInstruction(L3SubType.TTL_IN);
    }
@Test
    public void testCopyTtlInMethod() {
        final Instruction instruction = Instructions.copyTtlIn();
        final L3ModificationInstruction.ModTtlInstruction modTtlInstruction =
                checkAndConvert(instruction,
                                Instruction.Type.L3MODIFICATION,
                                L3ModificationInstruction.ModTtlInstruction.class);
        assertThat(modTtlInstruction.subtype(),
                   is(L3ModificationInstruction.L3SubType.TTL_IN));
    }