code: def unique_everseen(iterable, filterfalse_=itertools.filterfalse):
      
      # Itertools recipes:
      # https://docs.python.org/3/library/itertools.html#itertools-recipes
      seen = set()
      seen_add = seen.add
      for element in filterfalse_(seen.__contains__, iterable):
          seen_add(element)
          yield element
docs: Unique elements, preserving order.