code: func (t *Tree) DeepEach(cb func(*Tree)) {
  	t.lock.RLock()
  	defer t.lock.RUnlock()
  	t.deepEach(cb)
  }
docs: // DeepEach calls the provided callback for the receiver and then all of
  // its descendents in the tree, allowing an operation to be performed on
  // all modules in the tree.
  //
  // Parents will be visited before their children but otherwise the order is
  // not defined.