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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 img2img_transformer_base_tpu():
 """Hparams for training img2img_transformer on tpu."""

  hparams = img2img_transformer_base()
  update_hparams_for_tpu(hparams)
  hparams.batch_size = 2
  hparams.num_heads = 4   # heads are expensive on tpu
  hparams.num_decoder_layers = 8
  hparams.num_encoder_layers = 4
  hparams.shared_embedding_and_softmax_weights = False
  return hparams