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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def write_raw_text_to_files(all_files, urls_path, dataset_split, tmp_dir):
 """Write text to files."""


  def write_to_file(all_files, urls_path, tmp_dir, filename):
    """Write text to files."""
    with io.open(
        os.path.join(tmp_dir, filename + ".source"), "w",
        encoding="utf-8") as fstory:
      with io.open(
          os.path.join(tmp_dir, filename + ".target"), "w",
          encoding="utf-8") as fsummary:
        for example in example_generator(all_files, urls_path, sum_token=True):
          story, summary = _story_summary_split(example)
          fstory.write(story + "\n")
          fsummary.write(summary + "\n")

  if dataset_split == problem.DatasetSplit.TRAIN:
    filename = "cnndm.train"
  elif dataset_split == problem.DatasetSplit.EVAL:
    filename = "cnndm.dev"
  else:
    filename = "cnndm.test"

  tf.logging.info("Writing %s" % filename)
  write_to_file(all_files, urls_path, tmp_dir, filename)