code: def prompt_for_existing_session(self, sessions):
          
          if not sessions:
              return None
          print("Would you like to join a previous session or create a new session?")
          for index, session in enumerate(sessions):
              print(("{id} : {creator} started at {timestamp} ({hashid})"
                     .format(id=index+1, creator=session.get('creator'),
                             timestamp=session.get('created'), hashid=session.get('id'))))
          print("{new_id} : Create a new session with the current files?"
                .format(new_id=len(sessions)+1))
          desired = input("Type the number of the session you'd like to join: ")
          try:
              outcome = int(desired.strip())
          except:
              outcome = len(sessions)+1
              log.warning("Could not parse int for choice")
  
          if outcome >= len(sessions):
              log.info("Chose to start new session")
              return None
          else:
              log.info("Resuming session {}".format(outcome - 1))
              desired = sessions[outcome - 1]
              return session
docs: Prompt user if they want to resume an old session
          (or their partners session) or create a new session.