Utilities for working with data structures like lists, dicts and tuples.
Return from an iterable, a list of all the unique elements in the input, but maintaining the order in which they first appear.
Note: All elements in the input must be hashable for this routine to work, as it internally uses a set for efficiency reasons.
Flatten a list of lists (NOT recursive, only works for 2d lists).
Chop a sequence into chunks of the given size.