Common
```kotlin enum class TraverseDescendantsAction ``` Tree traversal actions for the traverseDescendantsIf related functions: - Continue - continue the traversal - SkipSubtreeAndContinue - continue the traversal BUT skip the matching node's subtree (this is a rarer case) - CancelTraversal - cancels the traversal (returns from function call) To see examples of all the actions, see TraversableModifierNodeTest. For a return/cancel example specifically, see traverseSubtreeWithSameKeyIf_cancelTraversalOfDifferentClassSameKey().