How would you effectively override a parent's computed iVar?

I'm trying to convert an existing Objective-C code into its Swift 3.0 equivalent.
I'm having trouble converting an Objective-C paradigm of defining the parent's declared getter (assessor) within its descendant; into its equivalent Swift 3.0's computed iVar paradigm.

Objective-C
Parent property:

@property(nonatomic, readonly) CGRect frameOfPresentedViewInContainerView;

Defining property within its descendant:

- (CGRect)frameOfPresentedViewInContainerView
{
    CGRect containerViewBounds = self.containerView.bounds;
    CGSize presentedViewContentSize = [self sizeForChildContentContainer:self.presentedViewController withParentContainerSize:containerViewBounds.size];

    // The presented view extends presentedViewContentSize.height points from
    // the bottom edge of the screen.
    CGRect presentedViewControllerFrame = containerViewBounds;
    presentedViewControllerFrame.size.height = presentedViewContentSize.height;
    presentedViewControllerFrame.origin.y = CGRectGetMaxY(containerViewBounds) - presentedViewContentSize.height;
    return presentedViewControllerFrame;
}

---

Swift 3.0
Parent property:

var frameOfPresentedViewInContainerView: CGRect { get }

When I attempt to define the value of 'frameOfPresentedViewInContainerView' via:

func frameOfPresentedViewInContainerView() -> CGRect {
        let containerViewBounds = self.containerView?.bounds;   // ...UIPresentationController  - iOS 10

}

I get the following compiler error:

Method 'frameOfPresentedViewInContainerView()' with Objective-C selector 'frameOfPresentedViewInContainerView' conflicts with getter for 'frameOfPresentedViewInContainerView' from superclass 'UIPresentationController' with the same Objective-C selector

Which makes sense and is obvious.
So what's the best way to override a parent's computed (getter) variable?

Note: the parent class is Apple's canned UIPresentationController.

You override the var, just as given in the Swift interface:

override var frameOfPresentedViewInContainerView: CGRect {