I only see a collection of exercises, but I don't see where is the proposed solution or how they are graded by difficulty or grouped by similarity. The link is

I only see a collection of exercises, but I don't see where is the proposed solution or how they are graded by difficulty or grouped by similarity. The link is the second set of exercises, there is part one. An example of exercise is this page is to define a function to remove spaces in subslists. It gives an example with input and expected output.