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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 MakeTargetMask(target, pad=0):
 """Create an attention mask to hide padding and future words."""

  target_mask = (target != pad)[ :, np.newaxis, :]
  target_dtype = target_mask.dtype
  causal_mask = onp.tril(onp.ones((1, target.shape[-1], target.shape[-1]),
                                  dtype=target_dtype), k=0)
  target_mask = target_mask & causal_mask
  return np.expand_dims(target_mask, axis=1)