void' is not an iterator interface type with collider "ERROR"

I was trying to remove a game object when you are interning a box collider, but my script is not working from some reason. I try to replace void whit IEnumerator but it give me a other error

“error CS1624: The body of DeathPit.OnTriggerEnter(UnityEngine.Collider)' cannot be an iterator block because void’ is not an iterator interface type”

So can someone help me ?

using UnityEngine;
using System.Collections;

public class DeathPit : MonoBehaviour {

	public GameObject sasa;
	
	void Start () 
	{
		sasa.SetActive (false);
	
	}
	

	void Update () 
	{
	
	}

	IEnumerator OnTriggerEnter(Collider broseidon)
	{



		if(broseidon.tag == "Player")
		{
			broseidon.transform.position = broseidon.GetComponent<Player>().checkPos;
			sasa.SetActive (true);
			yield return WaitForSeconds(0.5);
			sasa.SetActive (false);


		}
	}


}

Here is the script

That error should not appear for you because you have already changed void to IEnumerator in code provided in your question, thought you should have another error due to line #29, which should be:

yield return new WaitForSeconds(0.5f);