     }
     
     /**
+     Returns a Boolean value indicating whether the current queue contains the given requests.
+     
+     - Parameter requestKeyType: The type requestKey to find in the all current queue.
+     - Returns: `true` if one request with requestKey.Type was found in the current queue; otherwise, `false`.
+     */
+    public func containsRequest<T: Hashable>(requestKeyType: T.Type) -> Bool {
+        return (internalListRequest(requestKeyType: requestKeyType, onlyFirst: true)?.count ?? 0) > 0
+    }
+    
+    
+    /**
      Cancel all requests with equal this request.
      
      Signal cancel send to engine, but real canceled implementation in engine.

        return requestList[key]
    }
    
    
    private struct EmptyKey: Hashable {
        var hashValue: Int { return 0 }

     */
    public func cancelRequest(requestKey:AnyHashable?) {
        if let list = internalListRequest(requestKey: requestKey) {
            internalCancelRequests(ids: list)
        }
    }
    
    
    /**
     Cancel all requests with requestKey.Type.
     
     Signal cancel send to engine, but real canceled implementation in engine.
     
     - Parameter requestKeyType: The requestKey.Type to find in the current queue.
     */
    public func cancelRequest<T: Hashable>(requestKeyType: T.Type) {
        if let list = internalListRequest(requestKeyType: requestKeyType, onlyFirst: false) {
            internalCancelRequests(ids: list)
        }
    }
    
    
    /**
     Cancel all requests in current queue.
 
     Signal cancel send to engine, but real canceled implementation in engine.
     */
    public func cancelAllRequests() {
        var allList = Set<UInt64>()
        
