class_docstr: A BenchmarkProblem support multiple objectives. Rather than knowing each
  objective's optimal value we track a known maximum hypervolume computed from a
  given reference point.
code: def optimal_value(self) -> float:
      return self.maximum_hypervolume
  
imports: import abc
  from typing import Any, Dict, List, Optional, Protocol, runtime_checkable, Type
  from ax.core.metric import Metric
  from ax.core.objective import MultiObjective, Objective
  from ax.core.optimization_config import MultiObjectiveOptimizationConfig, ObjectiveThreshold, OptimizationConfig
  from ax.core.outcome_constraint import OutcomeConstraint
  from ax.core.parameter import ParameterType, RangeParameter
  from ax.core.runner import Runner
  from ax.core.search_space import SearchSpace
  from ax.core.types import ComparisonOp
  from ax.metrics.botorch_test_problem import BotorchTestProblemMetric
  from ax.runners.botorch_test_problem import BotorchTestProblemRunner
  from ax.utils.common.base import Base
  from ax.utils.common.typeutils import checked_cast
  from botorch.test_functions.base import BaseTestProblem, ConstrainedBaseTestProblem
  from botorch.test_functions.multi_objective import MultiObjectiveTestProblem
  from botorch.test_functions.synthetic import SyntheticTestFunction
label_desc: Use image node_id 2 for calling the MultiObjectiveBenchmarkProblem obj's underlying member method code with example usage: obj.optimal_value() and returns: self