Why would I need stacks and queues for Depth First Search?
I realized that I misread the assignment. It said: 
"Important note: Make sure to use the Stack, Queue and PriorityQueue data structures provided to you in util.py! These data structure implementations have particular properties which are required for compatibility with the autograder."
I had misread it as saying that I need to use all of them, when it is really saying that if I want to use them I should use their version.
I'm working on a project from the Berkeley AI curriculum, and they require me to use stacks, queues, and priority queues in my Depth First Graph Search implementation. I stored my fringe in a priority queue and my already visited states in a set. What am I supposed to use stacks and queues for in this assignment?
I'm not a student at Berkeley and I'm just using their curriculum for an independent study in high school and I got permission from my instructor to ask this online, so this is not a case of cheating on homework.