code: def testEval(self):
      trials = self.generate_trials(
          {
              "run": "PPO",
              "config": {
                  "foo": {"eval": "2 + 2"},
              },
          },
          "eval",
      )
      trials = list(trials)
      self.assertEqual(len(trials), 1)
      self.assertEqual(trials[0].config, {"foo": 4})
      self.assertEqual(trials[0].evaluated_params, {"foo": 4})
      self.assertEqual(trials[0].experiment_tag, "0_foo=4")
  
imports: import os
  import numpy
  import random
  import unittest
  import ray
  from ray.rllib import _register_all
  from ray import tune
  from ray.tune.result import DEFAULT_RESULTS_DIR
  from ray.tune.search import grid_search, BasicVariantGenerator
  from ray.tune.search.variant_generator import RecursiveDependencyError, _resolve_nested_dict
label_desc: Use image node_id 5 for calling the VariantGeneratorTest obj's underlying member method code with example usage: obj.testEval() without return types