code: def validate_customized_file(experiment_config, spec_key):
      '''
      check whether the file of customized tuner/assessor/advisor exists
      spec_key: 'tuner', 'assessor', 'advisor'
      '''
      if experiment_config[spec_key].get('codeDir') and \
          experiment_config[spec_key].get('classFileName') and \
          experiment_config[spec_key].get('className'):
          if not os.path.exists(os.path.join(
                  experiment_config[spec_key]['codeDir'],
                  experiment_config[spec_key]['classFileName'])):
              print_error('%s file directory is not valid!'%(spec_key))
              exit(1)
      else:
          print_error('%s file directory is not valid!'%(spec_key))
          exit(1f validate_customized_file(experiment_config, spec_key):
      '''
      check whether the file of customized tuner/assessor/advisor exists
      spec_key: 'tuner', 'assessor', 'advisor'
      '''
      if experiment_config[spec_key].get('codeDir') and \
          experiment_config[spec_key].get('classFileName') and \
          experiment_config[spec_key].get('className'):
          if not os.path.exists(os.path.join(
                  experiment_config[spec_key]['codeDir'],
                  experiment_config[spec_key]['classFileName'])):
              print_error('%s file directory is not valid!'%(spec_key))
              exit(1)
      else:
          print_error('%s file directory is not valid!'%(spec_key))
          exit(1)
docs: check whether the file of customized tuner/assessor/advisor exists
      spec_key: 'tuner', 'assessor', 'advisor'