Trigger a function on unsuscribe

Is there a way to trigger a function on when the client unsubscribes to a specific subscription
Something like this, but I know this doesn't work

` HomesSubscription: {
subscribe: (rootValue: any, args: any, context: any) => {
startHomeSub(context.token,context.env)
return pubsub.asyncIterator('Homes_Changed')
},
unsubscribe: () => {
stopHomeSub()
},
},`

The issue does not identify a file, test, or implementation entry point. First clarify the expected unsubscribe lifecycle and scope, then locate the subscription handling code and add a focused test showing that the requested callback runs when a client unsubscribes.

Written by the indexing model from the issue text.