Variables per ChatSession?

[gururise]

For each chat session, the Chatbot may be speaking to a different user (or it may be the same user who came back later). I want to have a userId variable defined for each chat session. Is this possible?

For example if I instantiate and set userId = '3423423'
Its not clear in the documentation whether userId will be unique to each Chat Session, or whether I can only have one userId and it will be shared across the enitre Chat Flow?