docstr: test for json2parameter
          
code: def test_json2parameter(self):
      """test for json2parameter"""
      json_search_space = {
          "optimizer": {"_type": "choice", "_value": ["Adam", "SGD"]},
          "learning_rate": {
              "_type": "choice",
              "_value": [0.0001, 0.001, 0.002, 0.005, 0.01],
          },
      }
      parameter = {
          "root[learning_rate]-choice": 2,
          "root[optimizer]-choice": 0,
      }
      search_space_instance = json2parameter(
          json_search_space, parameter
      )
      self.assertEqual(search_space_instance["optimizer"]["_index"], 0)
      self.assertEqual(
          search_space_instance["optimizer"]["_value"], "Adam"
      )
      self.assertEqual(
          search_space_instance["learning_rate"]["_index"], 2
      )
      self.assertEqual(
          search_space_instance["learning_rate"]["_value"], 0.002
      )
  
file_path: nni/test/ut/sdk/test_hyperopt_tuner.py
imports: from unittest import TestCase, main
  import hyperopt
  from nni.algorithms.hpo.hyperopt_tuner import json2space, json2parameter, json2vals, HyperoptTuner
label_desc: Use image node_id 2 for calling the HyperoptTunerTestCase obj's underlying member method code with example usage: obj.test_json2parameter() without return types