code: def flatten(listOfLists):
      """Return an iterator flattening one level of nesting in a list of lists.
  
          >>> list(flatten([[0, 1], [2, 3]]))
          [0, 1, 2, 3]
  
      See also :func:`collapse`, which can flatten multiple levels of nesting.
  
      """
      return chain.from_iterable(listOfLists)
  
imports: import warnings
  from collections import deque
  from itertools import chain, combinations, count, cycle, groupby, islice, repeat, starmap, tee, zip_longest
  import operator
  from random import randrange, sample, choice
label_desc: Use image node_id 11 for calling a global function with example usage: flatten(listOfLists) and returns: chain