docstr: Assert that custom nested parameter columns are printed correctly
docstr_tok: ["Assert","that","custom","nested","parameter","columns","are","printed","correctly"]
code: def testBestTrialStr(self):
      """Assert that custom nested parameter columns are printed correctly"""
      config = {
          "nested": {"conf": "nested_value"},
          "toplevel": "toplevel_value",
      }
  
      trial = Trial("", config=config, stub=True)
      trial.run_metadata.last_result = {
          "metric": 1,
          "config": config,
          "nested": {"metric": 2},
      }
  
      result = _best_trial_str(trial, "metric")
      self.assertIn("nested_value", result)
  
      result = _best_trial_str(
          trial, "metric", parameter_columns=["nested/conf"]
      )
      self.assertIn("nested_value", result)
  
      # Test that this works with a nested metric
      result = _best_trial_str(
          trial, "nested/metric", parameter_columns=["nested/conf"]
      )
      self.assertIn("nested_value", result)
  
imports: import collections
  import os
  import regex
  import unittest
  from unittest.mock import MagicMock, Mock, patch
  import pytest
  import numpy
  from ray import train, tune
  from ray._private.test_utils import run_string_as_driver
  from ray.tune.progress_reporter import CLIReporter, JupyterNotebookReporter, ProgressReporter, _fair_filter_trials, _best_trial_str, _detect_reporter, _time_passed_str, _trial_progress_str, TuneReporterBase, _max_len
  from ray.tune.result import AUTO_RESULT_KEYS
  from ray.tune.experiment.trial import Trial
label_desc: Use image node_id 7 for calling the ProgressReporterTest obj's underlying member method code with example usage: obj.testBestTrialStr() without return types