 internal extension MotionController {
     // should call this after `prepareTransitionPairs` & before `processContext`
     func insert<T>(preprocessor: MotionPreprocessor, before: T.Type) {
-        guard var v = preprocessors else {
-            return
-        }
-        
-        let i = v.index { $0 is T } ?? v.count
+        guard var p = preprocessors else {
+            return
+        }
+        
+        let i = p.index { $0 is T } ?? p.count
         preprocessor.context = context
-        v.insert(preprocessor, at: i)
-    }
-}
+        p.insert(preprocessor, at: i)
+    }
+}

        }
        
        var t: TimeInterval = 0
        var v = false
        
        if let a = animators, let tp = transitionPairs {
            for (i, x) in a.enumerated() {
                let d = x.animate(fromViews: tp[i].0, toViews: tp[i].1)
                
                if d == .infinity {
                    v = true
                } else {
                    t = max(t, d)
                }

        
        totalDuration = t
        
        if b {
            update(elapsedTime: 0)
        } else {
            complete(after: t, isFinished: true)
