transitionCoordinator return nil for custom container view controller in iOS8

when reference transitionCoordinator on child vc, it used to called transitionCoordinator on custom container class in iOS7, but in iOS8 this wasn't the case. Now it return nil and I have no clue what should I change to make this work.

I guess its about UIPresentationController introduced in iOS8, but can't find proper implementation for custom container view controller.

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