What's supposed to be into the request.session_id?

Hello there,

I'm using your code as basis for deploying a bot with Telegram. But I couldn't understand what is supposed to be into the `request.session_id` variable (bot.py, line 14). I guess is something related to DialogFlow, but I'm not quite sure and nothing was mentioned on the wiki (o at least something I could find). 

Best regards and thanks for this bot bootstrap!