how to cancel subscription to window.cookieStore.addEventListener(‘change’, ) in angular service

I have created an angular service which can listen to cookie changes by leveraging the CookieStore Api.
My current code looks as follows:

type CookieChangeType = {
    name: string,
    value: string,
    expires: Date,
    domain: string,
}

interface CookieChangeEvent extends Event {
    changed: CookieChangeType[]
}

type CookieStore = {
    addEventListener: Window["addEventListener"]
}

declare global {
    interface Window {
        cookieStore: CookieStore;
        addEventListener(type: String, listener: (this: Window, ev: CookieChangeEvent) => any, useCapture?: boolean): void;
    }
} 

export class CookieConsentCommonsService {
     
    
    subscribeToConsentCookieChange(callback: () => void): void {
            window.cookieStore.addEventListener('change', (event: CookieChangeEvent) => {
                console.log(`Cookie changed: ${change.name} = ${change.value}`);
                callback();            
            });
    }
}

This code works as expected.
On the top of that I would like to be able to cancel the subscription. I have tried to store the subscription for later :

            const sub = window.cookieStore.addEventListener( ...);
            console.log("sub " + sub)

But there is no return from this code and the output message is:

sub undefined

How can I retrieve a reference for created subscription and later on use it to cancel the subscription?