code: def testRefValue(self):
      config = {
          "param1": "ok",
          "param2": ["not ok", Dummy("ok")],
          "param3": {
              "param4": Dummy("not ok"),
          },
      }
  
      replaced = create_resolvers_map()
      config = inject_placeholders(config, replaced)
  
      self.assertEqual(config["param2"][1][0], _RefResolver.TOKEN)
      self.assertEqual(
          config["param3"]["param4"][0], _RefResolver.TOKEN
      )
  
      resolve_placeholders(config, replaced)
  
      self.assertEqual(config["param2"][1].value, "ok")
      self.assertEqual(config["param3"]["param4"].value, "not ok")
  
imports: import numpy
  import unittest
  from ray import tune
  from ray.tune.impl.placeholder import inject_placeholders, resolve_placeholders, create_resolvers_map, _FunctionResolver, _RefResolver
  from ray.tune.search.sample import Float, Integer
label_desc: Use image node_id 8 for calling the PlaceholderTest obj's underlying member method code with example usage: obj.testRefValue() without return types