PrepareFrameForChild()
This callback method requests a frame to be prepared for indirect transmission to a given sleepy child.
HandleSentFrameToChild()
This callback method notifies the end of indirect frame transmission to a child.
HandleFrameChangeDone()
This callback method notifies that a requested frame change from `RequestFrameChange()` is processed. This callback indicates to the next layer that the indirect frame/message for the child can be safely updated.