I'm getting an error CS1041: Identifier expected for my script?

So I'm following this person's script for AudioFadeOut: https://forum.unity3d.com/threads/fade-out-audio-source.335031/ and I'm going through and fixing the errors that pop up but one has me stumped.

Assets/Scripts/AudioFadeOut.cs(6,44): error CS1041: Identifier expected

This is what my current script looks like:

 using UnityEngine;
 using System.Collections;
 
 public static class AudioFadeOut : MonoBehaviour {
     
     public static IEnumerator FadeOut (AudioSource, float FadeTime) {
         float startVolume = AudioSource.volume;
 
         while (AudioSource.volume > 0){
             AudioSource.volume -= startVolume * Time.deltaTime / FadeTime;
 
             yield return null;
         }
 
         AudioSource.Stop ();
         AudioSource.volume = startVolume;
     }
 
 }

Now I know that there's something wrong with line 6 that's causing this error but no matter what I try, this one is very stubborn. Can a pro point out where I've gone wrong or what I've missed here? I would greatly appreciate any and all help :)