If you scroll to the bottom of the Snips jython tutorial I wrote (Tutorial for using the Snips Voice Assistant with Jython and Mqtt for switching and dimming lights) you can see how to do it. But the basis is to extract the session ID of the original message object to a variable and than publish a session end with the extracted session ID using the mqtt publish action in the correct format to hermes/dialogueManager/endSession.
You can find details on the session ID here:
https://docs.snips.ai/reference/dialogue#intent
and on the session end here:
https://docs.snips.ai/reference/dialogue#end-session
Best regards Johannes