Weight-level magnitude pruning.

def weight(w, sparsity):
  """Weight-level magnitude pruning."""
  w_shape = common_layers.shape_list(w)
  k = int(np.prod(w_shape[:-1]))
  count = tf.to_int32(k * sparsity)
  mask = common_layers.weight_targeting(w, count)
  return (1 - mask) * w