code: def test_truncate_empty_pool(self, space, monkeypatch):
      lineages = build_lineages_for_exploit(space, monkeypatch)
  
      exploit = self.constructor(candidate_pool_ratio=0.0001)
  
      selected_trial = exploit._truncate(
          numpy.random.RandomState(1),
          lineages.get_trials_at_depth(1)[-1],
          lineages.get_trials_at_depth(1),
      )
  
      assert selected_trial is None
  
imports: import numpy
  import pytest
  from base import RNGStub, TrialStub
  from orion.algo.pbt.exploit import BacktrackExploit, PipelineExploit, TruncateExploit
  from orion.algo.pbt.pbt import Lineages
label_desc: Use image node_id 5 for calling the TruncateGenericTests obj's underlying member method code with example usage: obj.test_truncate_empty_pool(space, monkeypatch) without return types