code: def test_generate_offspring_unknown_trial(self, space: Space):
      pbt = _create_algo(space).unwrap(PBT)
      trial = sample_trials(pbt.space, 1)[0]
      with pytest.raises(
          RuntimeError, match="Trying to fork a trial that"
      ):
          pbt._generate_offspring(trial)
  
imports: from __future__ import annotations
  import functools
  import logging
  from typing import ClassVar
  import numpy
  import pytest
  from base import ExploitStub, ExploreStub, sample_trials
  from pytest_mock import MockerFixture
  from orion.algo.pbt.pbt import PBT, compute_fidelities
  from orion.algo.space import Space
  from orion.core.worker.primary_algo import SpaceTransform, create_algo
  from orion.core.worker.transformer import ReshapedSpace, TransformedSpace
  from orion.core.worker.trial import Trial
  from orion.testing.algo import BaseAlgoTests, TestPhase
label_desc: Use image node_id 1 for calling the TestPBTSuggest obj's underlying member method code with example usage: obj.test_generate_offspring_unknown_trial(space) without return types