No uniform Graph class in BFS/ And find #nodes per level

I just wanted to say I find it rather irritating that there is no uniform graph implementation…you give us a graph implementation in the Graph class where adjacency lists are represented as double sided linkedlists then in the question where we need to calculate nodes given a certain level, you give us another DIFFERENT implementation of graph class where adjacency lists are simple lists of lists (linkedlists)…can we have ONE implementation and just stick to it? this feels like 10 people contributed to these solutions with NO cohesion at all…how are people expected to learn?

like the whole point of learning BFS is being able to go into a question where we need to find # of nodes per level and return that count…we’re meant to take our BFS algo and tweak it as such so that we can find that…how are we to do this when you keep changing the implementation on us lol…i know these are meant to be challenging but stil…