def unique_everseen(iterable, key=None):
"""List unique elements, preserving order. Remember all elements ever seen.
See https://docs.python.org/3/library/itertools.html#itertools-recipes
def unique_everseen(iterable, key=None):
"""List unique elements, preserving order. Remember all elements ever seen.
See https://docs.python.org/3/library/itertools.html#itertools-recipes