@Override
 ChannelBuffer serialize(Message header) {
   assert header.isInitialized();
   final GetMasterRegistrationRequestPB.Builder builder =
       GetMasterRegistrationRequestPB.newBuilder();
   return toChannelBuffer(header, builder.build());
 }
 @Override
 ChannelBuffer serialize(Message header) {
   assert header.isInitialized();
   final IsAlterTableDoneRequestPB.Builder builder = IsAlterTableDoneRequestPB.newBuilder();
   TableIdentifierPB tableID = TableIdentifierPB.newBuilder().setTableName(name).build();
   builder.setTable(tableID);
   return toChannelBuffer(header, builder.build());
 }