> I mean, how else would you call the arguments of > splitAt :: Eq a => a -> [a] -> [[a]]

Those don't seem to be names of parameters, but rather of types. It's missing parameter names entirely.

I spent a good 2 minutes looking at that signature trying to figure it out (and I've read some Haskell tutorials so I'm at least familiar with the syntax). This would've helped:

    def split_by<T>(separator: T, list: List[T]) -> List[List[T]]

`sep`, `separator`, `delim`, `delimiter` would've been good names.