Google review manager issue

I added the google play core package as instructed in the repo, and added the code according to the documentation here

I receive the following error: CS0246: The type or namespace name 'PlayAsyncOperation<,>' could not be found (are you missing a using directive or an assembly reference?)

This error shows at _reviewManager.RequestReviewFlow(); and _reviewManager.LaunchReviewFlow(_playReviewInfo)

Any idea what could be the issue?

My full code:

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using Google.Play.Review;
 
 public class ReviewCodes : MonoBehaviour
 {
     private ReviewManager _reviewManager;
     private PlayReviewInfo _playReviewInfo;
 
 
     // Start is called before the first frame update
     void Start()
     {
         StartCoroutine(RequestReviews());
     }
 
     // Update is called once per frame
     void Update()
     {
         
     }
 
     IEnumerator RequestReviews()
     {
         // Create instance of ReviewManager
         _reviewManager = new ReviewManager();
 
         var requestFlowOperation = _reviewManager.RequestReviewFlow();
         yield return requestFlowOperation;
         if (requestFlowOperation.Error != ReviewErrorCode.NoError)
         {
             // Log error. For example, using requestFlowOperation.Error.ToString().
             yield break;
         }
         _playReviewInfo = requestFlowOperation.GetResult();
 
         var launchFlowOperation = _reviewManager.LaunchReviewFlow(_playReviewInfo);
         yield return launchFlowOperation;
         _playReviewInfo = null; // Reset the object
         if (launchFlowOperation.Error != ReviewErrorCode.NoError)
         {
             // Log error. For example, using requestFlowOperation.Error.ToString().
             yield break;
         }
         // The flow has finished. The API does not indicate whether the user
         // reviewed or not, or even whether the review dialog was shown. Thus, no
         // matter the result, we continue our app flow.
     }
 }