// async setLens function
...
const applyLensPromise = session.applyLens(lens); // camerakit session
const lensLoadedPromise = this.waitForSessionEvent(LensStep.SessionEvents.LENS_LOADED); // check bellow

await Promise.allSettled([
    applyLensPromise,
    // Event is not getting fired until session is playing ↓
    session.playing || playIfNotPlaying ? lensLoadedPromise : undefined,
    // When we dont need to run play ↓
    !session.playing && playIfNotPlaying ? this.play() : undefined,
]);
...

// waitForSessionEvent function for above
waitForSessionEvent(eventType: string): Promise < any > {
    return new Promise(resolve =>
        // see here we used session.stateTarget.addEventListener, but stateTarget is actually private!
        this.session.stateTarget.addEventListener(eventType, (event: unknown) => resolve(event), {
            once: true,
        }),
    );
}