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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 denoise_z15():
 """Replace tokens instead of masking."""

  hparams = xmoe2_dense_0()
  hparams.decoder_type = "denoising"
  hparams.noising_spec_train = {"type": "random_zipfian", "prob": 0.15}
  hparams.noising_use_eval_during_train = 0.25
  return hparams