IE numerator Scripting problem C#

I want to have ChestOpen set active after 1 second PLz help

using UnityEngine;
using System.Collections;

public class Keyandlock : MonoBehaviour 
{
	public GameObject Key;
	public GameObject ChestLid;
	public GameObject ChestOpen;
	public GameObject Chestanim;
	public GameObject Open;
	public GameObject ChestContence;

	void Start ()
	{
		//Test
		StartCoroutine(Test());

		ChestLid.SetActive (true);
		ChestOpen.SetActive (false);
		Chestanim.SetActive (false);
		Open.SetActive (false);
		ChestContence.SetActive (false); 
	}
		
	void OnTriggerEnter(Collider other) 
	{
		if (other.gameObject.tag == "Key") 
		{
			Debug.Log ("Detected");
			ChestContence.SetActive (true);
			Key.SetActive (true);
			ChestLid.SetActive (false);
			Open.SetActive (true);
			//Animation
			Chestanim.SetActive (true);
			//Wait Until aim is done then open chest

			IEnumerator Test()
			{
				yield return new WaitForSeconds (1);
				ChestOpen.SetActive (true);
			}
		}
	}
}

Your “Test” coroutine is a method. You can’t declare methods inside methods. It has to be declared inside your class. Also “Test” is a bad name. You should use a descriptive name like this:

using UnityEngine;
using System.Collections;

public class Keyandlock : MonoBehaviour 
{
    public GameObject Key;
    public GameObject ChestLid;
    public GameObject ChestOpen;
    public GameObject Chestanim;
    public GameObject Open;
    public GameObject ChestContence;

    void Start ()
    {
        ChestLid.SetActive (true);
        ChestOpen.SetActive (false);
        Chestanim.SetActive (false);
        Open.SetActive (false);
        ChestContence.SetActive (false); 
    }
         
    void OnTriggerEnter(Collider other) 
    {
        if (other.gameObject.tag == "Key") 
        {
            Debug.Log ("Detected");
            ChestContence.SetActive (true);
            Key.SetActive (true);
            ChestLid.SetActive (false);
            Open.SetActive (true);
            //Animation
            Chestanim.SetActive (true);
            
            StartCoroutine(OpenChestDelayed());
        }
    }
    IEnumerator OpenChestDelayed()
    {
        yield return new WaitForSeconds (1);
        ChestOpen.SetActive (true);
    }
}