old_contents: 
  def pick(iterable):
  	return iter(iterable).next()
  
  
new_contents: 
  def pick(iterable):
  	return iter(iterable).next()
  
  def iter_by_n(iterable, n):
          ret = []
          it = iter(iterable)
          while True:
                  while len(ret) < n:
                          try:
                                  ret.append(next(it))
                          except StopIteration:
                                  if ret:
                                          yield ret
                                  return
                  yield ret
                  ret = []
  
subject: add iter_by_n