code: def _state_value(self, state: State) -> float:
      return (
          0.0
          if (state is None or state.is_terminal)
          else (
              0.0
              if state not in self._state_values
              else self._state_values[state]
          )
      )
  
imports: import pickle
  from functools import reduce
  from typing import List, Mapping, Sequence
  import torch
  from reagent.ope.estimators.sequential_estimators import Model, RLPolicy, State, ValueFunction
  from reagent.ope.estimators.types import Action, ActionDistribution, ActionSpace
  from reagent.ope.test.envs import Environment, PolicyLogGenerator
  from reagent.ope.utils import RunningAverage
label_desc: Use image node_id 2 for calling the TabularValueFunction obj's underlying member method code with example usage: obj._state_value(state) and returns: unknown