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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 value_net(rng_key, batch_observations_shape, num_actions, bottom_layers=None):
 """A value net function."""

  del num_actions

  if bottom_layers is None:
    bottom_layers = []
  bottom_layers.extend([
      layers.Dense(1),
  ])
  net = layers.Serial(*bottom_layers)
  return net.initialize(batch_observations_shape, rng_key), net