@Override
  public void fromData(DataInput in,
      DeserializationContext context) throws IOException, ClassNotFoundException {
    // should never be called since the special DataSerializer.readRegion is used.
    throw new UnsupportedOperationException("fromData is not implemented");
  }
Returns the serial number which identifies the static order in which this region was created in
relation to other regions or other instances of this region during the life of this JVM.
geode-core/src/main/java/org/apache/geode/internal/cache/AbstractRegion.java