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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 concat_generator(filename, up_threshold, low_threshold=10):
 """Generate concatenated lines from file upto up_threshold characters."""

  txt = ""
  for line in tf.gfile.Open(filename):
    line = line.strip()
    if len(txt) + len(line) + 1 >= up_threshold:
      ret = txt
      txt = ""
      # We don't yield very short long parts to prevent noisy examples.
      if len(ret) > low_threshold and len(ret) < up_threshold:
        yield {"targets": ret}

    if not txt:
      txt = line
    else:
      txt = " ".join([txt, line])