NSSplitViewItem.isCollapsed ignores animation durations - swift

Question

I am trying to collapse an NSSplitViewItem like so
NSAnimationContext.runAnimationGroup({ context in
context.duration = 0.1
context.allowsImplicitAnimation = true
searchItem.isCollapsed = collapsed
}, completionHandler: {
// do stuff
})
No matter what I set for the duration, the animation duration of the collapse animation does not change.
Setting the duration on a CATransaction also does not work.
Checking the header files it mentions this:
The exact animation used can be customized by setting it
in the -animations dictionary with a key of "collapsed".
That raises even more questions. When do I set this animation? What keypath do I animate with this animation? What to/from values does it expect? etc... All I want to do is change its duration.
Solution:
As per #Loengard's answer this is what I went with
NSAnimationContext.runAnimationGroup { _ in
let animation = CABasicAnimation(keyPath: nil)
animation.duration = 0.1
searchItem.animations["collapsed"] = animation
searchItem.animator().isCollapsed = collapsed
}

Answer 1

The dictionary the header file refers to is searchItem.animations. You don't need to specify fromValue or toValue, just customize duration like this:
NSAnimationContext.runAnimationGroup({ context in
context.duration = 0.1
context.allowsImplicitAnimation = true
let collapseAnimation = CABasicAnimation(keyPath: "collapsed")
collapseAnimation.duration = 0.1
var existingAnimations = searchItem.animations
existingAnimations["collapsed"] = collapseAnimation
searchItem.animations = existingAnimations
searchItem.isCollapsed = !searchItem.isCollapsed
}) { }