I am working on a mongodb connector for the Apache Flink project - https://flink.apache.org/

Internally, Flink is using java serialization to save the records it is working on in a state which in turn used to recover from failures etc, as well as for passing records between different tasks in the pipeline.
I have noticed the mongodb client model classes are not Serializable for instance, classes such as WriteModel https://github.com/mongodb/mongo-java-driver/blob/master/driver-core/src/main/com/mongodb/client/model/WriteModel.java and its subclasses or the different Options like ReplaceOptions https://github.com/mongodb/mongo-java-driver/blob/master/driver-core/src/main/com/mongodb/client/model/ReplaceOptions.java

is there a reason for these classes to not be declared Serializable? Is there a way to contribute to the Java driver project by opening a PR that addresses this?