Overload Method problem

Anyone know this problem? Because in tutorial no problem founded

 using UnityEngine;
 using System.Collections;
 
 public class ads : MonoBehaviour {
     private const string AD_UNIT_ID="xxxxxxxxx";
     private AdMobPlugin admob;
 
     public bool hidden = true;
     // Use this for initialization
     void Awake () {
     
     }
     
     // Update is called once per frame
     void Start () {
         admob = GetComponent<AdMobPlugin>();
         admob.CreateBanner(AD_UNIT_ID, AdMobPlugin.AdSize.SMART_BANNER, true); // error message No overload method, takes 3 arguments
         admob.RequestAd();
         admob.ShowBanner();
 
     }
 }

Can anyone help me? thanks ;)