The PEP 572 endgame

I remember that for Python3, Guido wanted to remove map, filter, and reduce because he didn't think they were very Pythonic (in favor of just using list comprehensions). Personally, I don't find Python's list comprehensions to be that crazy in practice. One issue I do have is the ambiguity of where an `if` fragment attaches within the loop, but I think the Python answer there is "decompose your code more" to make it simpler in the first place. Especially now that they form can generators rather than structures directly.