     
     static let sharedManager = VoiceMessageAttachmentCacheManager()
     
-    private var completionCallbacks = [CompletionCallbackKey: [CompletionWrapper]]()
+    private var completionCallbacks = [String: [CompletionWrapper]]()
     private var samples = [String: [Int: [Float]]]()
     private var durations = [String: TimeInterval]()
     private var finalURLs = [String: URL]()
     
-    private let workQueue: DispatchQueue
-    
     private init() {
-        workQueue = DispatchQueue(label: "io.element.VoiceMessageAttachmentCacheManager.queue", qos: .userInitiated)
+        
     }
     
     func loadAttachment(_ attachment: MXKAttachment, numberOfSamples: Int, completion: @escaping (Result<VoiceMessageAttachmentCacheManagerLoadResult, Error>) -> Void) {

            }
        }
        
        self.completionCallbacks[callbackKey] = nil
    }
}

    }
}

struct VoiceMessageAttachmentCacheManagerLoadResult {
    let eventIdentifier: String
    let url: URL
