class_docstr: A network with two linear layers, for policy and value respectively.
code: def __init__(self, num_actions: int):
      super().__init__(name="policy_value_network")
      self._policy_layer = snt.Linear(num_actions)
      self._value_layer = snt.Linear(1)
  
imports: from typing import Sequence, Tuple
  from acme import specs
  from acme.tf import utils
  import numpy
  import sonnet
  import tensorflow
  from absl.testing import absltest
  from absl.testing import parameterized
label_desc: Use image node_id 1 to create a new PolicyValueHead object from inherited base classes: snt with example: obj = PolicyValueHead(num_actions)