code: def parallel_iterate(source_iterators: Sequence[Iterator[Optional[Any]]],
                       target_iterator: Iterator[Optional[Any]],
                       skip_blanks: bool = True):
      
      num_skipped = 0
      while True:
          try:
              sources = [next(source_iter) for source_iter in source_iterators]
              target = next(target_iterator)
          except StopIteration:
              break
          if skip_blanks and (any((s is None for s in sources)) or target is None):
              num_skipped += 1
              continue
          check_condition(are_none(sources) or are_token_parallel(sources), "Source sequences are not token-parallel: %s" % (str(sources)))
          yield sources, target
  
      if num_skipped > 0:
          logger.warning("Parallel reading of sequences skipped %d elements", num_skipped)
  
      check_condition(
          all(next(cast(Iterator, s), None) is None for s in source_iterators) and next(cast(Iterator, target_iterator),
                                                                                        None) is None,
          "Different number of lines in source(s) and target iterables.")
docs: Yields parallel source(s), target sequences from iterables.
      Checks for token parallelism in source sequences.
      Skips pairs where element in at least one iterable is None.
      Checks that all iterables have the same number of elements.
      Can optionally continue from an already-begun iterator.
  
      :param source_iterators: A list of source iterators.
      :param target_iterator: A target iterator.
      :param skip_blanks: Whether to skip empty target lines.
      :return: Iterators over sources and target.