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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 imagetransformer_sep_channels_8l_tpu():
 """Hparams for training imagetransformer on tpu."""

  hparams = imagetransformer_sep_channels_8l()
  update_hparams_for_tpu(hparams)
  hparams.batch_size = 4
  hparams.num_heads = 4   # heads are expensive on tpu
  hparams.shared_embedding_and_softmax_weights = False
  return hparams