code: def _get_trial_values(trials: list[FrozenTrial]) -> list[float]:
      values = []
      for t in trials:
          assert t.value is not None
          values.append(t.value)
      return values
  
file_path: optuna/tests/terminator_tests/improvement_tests/test_preprocessing.py
imports: from __future__ import annotations
  from unittest import mock
  import numpy
  import pytest
  from optuna.distributions import CategoricalDistribution
  from optuna.distributions import FloatDistribution
  from optuna.distributions import IntDistribution
  from optuna.study._study_direction import StudyDirection
  from optuna.terminator.improvement import _preprocessing
  from optuna.trial import create_trial
  from optuna.trial import FrozenTrial
label_desc: Use image node_id 1 for calling a global function with example usage: _get_trial_values(trials) and returns: values