public static Instruction pushMpls() {
        return new L2ModificationInstruction.ModMplsHeaderInstruction(
                L2ModificationInstruction.L2SubType.MPLS_PUSH,
                                          EthType.EtherType.MPLS_UNICAST.ethType());
    }
@Test
    public void testPushMplsMethod() {
        final Instruction instruction = Instructions.pushMpls();
        final L2ModificationInstruction.ModMplsHeaderInstruction pushHeaderInstruction =
                checkAndConvert(instruction,
                                Instruction.Type.L2MODIFICATION,
                                L2ModificationInstruction.ModMplsHeaderInstruction.class);
        assertThat(pushHeaderInstruction.ethernetType().toString(),
                   is(EthType.EtherType.MPLS_UNICAST.toString()));
        assertThat(pushHeaderInstruction.subtype(),
                   is(L2ModificationInstruction.L2SubType.MPLS_PUSH));
    }