Since we have used ExperimenterIdMeterSubTypeSerializerKey as MeterBandSerializer's key, in order to avoid the occurrence of an error, we should add a new function(public void registerMeterBandSerializer(final ExperimenterIdMeterSubTypeSerializerKey<MeterBandExperimenterCase> key,
final OFSerializer<MeterBandExperimenterCase> serializer)) and discard the old function( public void registerMeterBandSerializer(final ExperimenterIdSerializerKey<MeterBandExperimenterCase> key,
final OFSerializer<MeterBandExperimenterCase> serializer))