Only make sense when the message has implemented the hashCode()
Otherwise, it will use Object.hashCode(), which will not return
same hash code after serialization and deserialization.
Linear Supertypes
Partitioner, Serializable, Serializable, AnyRef, Any
Only make sense when the message has implemented the hashCode() Otherwise, it will use Object.hashCode(), which will not return same hash code after serialization and deserialization.