         }
     }
     
-    override var isFinished: Bool {
+    override open var isFinished: Bool {
         return _finished
     }
     
-    override func start()
+    override open func start()
     {
         _executing = true
         execute()
     }
     
-    func execute()
+    open func execute()
     {
         // Execute your async task here.
     }
     
-    func finish()
+    open func finish()
     {
         _executing = false
         _finished = true


import Foundation

class ConcurrentOperation: Operation
{
    override var isAsynchronous: Bool {
        return true
    }
    

        }
    }
    
    override open var isExecuting: Bool {
        return _executing
    }
    
