class_docstr: Learner for PPO.
code: def get_variables(
      self, names: List[str]
  ) -> List[networks_lib.Params]:
      variables = self._cached_state
      return [getattr(variables, name) for name in names]
  
imports: from typing import Dict, Iterator, List, NamedTuple, Optional, Tuple
  import acme
  from acme import types
  from acme.agents.jax.ppo import networks
  from acme.agents.jax.ppo import normalization
  from acme.jax import networks
  from acme.jax.utils import get_from_first_device
  from acme.utils import counting
  from acme.utils import loggers
  import jax
  import jax.numpy
  import optax
  import reverb
  import rlax
label_desc: Use image node_id 3 for calling the PPOLearner obj's underlying member method code with example usage: obj.get_variables(names) and returns: unknown