docstr: test for json2space
          
code: def test_json2space(self):
      """test for json2space"""
      json_search_space = {
          "optimizer": {"_type": "choice", "_value": ["Adam", "SGD"]},
          "learning_rate": {
              "_type": "choice",
              "_value": [0.0001, 0.001, 0.002, 0.005, 0.01],
          },
      }
      search_space_instance = json2space(json_search_space)
      self.assertIsInstance(
          search_space_instance["optimizer"], hp.pyll.base.Apply
      )
      self.assertIsInstance(
          search_space_instance["learning_rate"], hp.pyll.base.Apply
      )
  
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 1 for calling the HyperoptTunerTestCase obj's underlying member method code with example usage: obj.test_json2space() without return types