code: public byte[] serialize( final MemcachedBackupSession session, final byte[] attributesData ) {
          final byte[] sessionData = serializeSessionFields( session );
          final byte[] result = new byte[ sessionData.length + attributesData.length ];
          System.arraycopy( sessionData, 0, result, 0, sessionData.length );
          System.arraycopy( attributesData, 0, result, sessionData.length, attributesData.length );
          return result;
      }
docs: Serialize session fields to a byte[] and create a byte[] containing both the
  serialized byte[] of the session fields and the provided byte[] of the serialized
  session attributes.
  
  @param session its fields will be serialized to a byte[]
  @param attributesData the serialized session attributes (e.g. from {@link #serializeAttributes(MemcachedBackupSession, ConcurrentMap)})
  @return a byte[] containing both the serialized session fields and the provided serialized session attributes