Savepoints with bootstraping a datastream function

[Rakshit Ramesh]

I'm trying to bootstrap state into a KeyedProcessFunction equivalent that
takes in
a DataStream but I'm unable to find a reference for the same.
I found this gist
https://gist.github.com/alpinegizmo/ff3d2e748287853c88f21259830b29cf
But it seems to only apply for DataSet.
My usecase is to manually trigger a Savepoint into s3 for later reuse.
I'm also guessing that checkpoints can't be stored in rocksdb or s3 for
later reuse.