code: func (g *AcyclicGraph) Walk(cb WalkFunc) tfdiags.Diagnostics {
  	defer g.debug.BeginOperation(typeWalk, "").End("")
  
  	w := &Walker{Callback: cb, Reverse: true}
  	w.Update(g)
  	return w.Wait()
  }
docs: // Walk walks the graph, calling your callback as each node is visited.
  // This will walk nodes in parallel if it can. The resulting diagnostics
  // contains problems from all graphs visited, in no particular order.