code: public static <T> TypeSerializerSnapshot<T> snapshotBackwardsCompatible(TypeSerializer<T> originatingSerializer) {
  		return configureForBackwardsCompatibility(originatingSerializer.snapshotConfiguration(), originatingSerializer);
  	}
docs: Takes a snapshot of the given serializer. In case where the snapshot
  is still extending the old {@code TypeSerializerConfigSnapshot} class, the snapshot
  is set up properly (with its originating serializer) such that the backwards
  compatible code paths work.