code: def _check_strategy(strategy):
      """Assert strategy value.
  
      Parameters
      ----------
      strategy : str
          strategy of how to evaluate a forecaster
          must be in "refit", "update" , "no-update_params"
  
      Raises
      ------
      ValueError
          If strategy value is not in expected values, raise error.
      """
      valid_strategies = ("refit", "update", "no-update_params")
      if strategy not in valid_strategies:
          raise ValueError(
              f"`strategy` must be one of {valid_strategies}"
          )
  
file_path: sktime/sktime/forecasting/model_evaluation/_functions.py
imports: import time
  import warnings
  from typing import Dict, List, Optional, Union
  import numpy
  import pandas
  from sktime.datatypes import check_is_scitype, convert_to
  from sktime.exceptions import FitFailedWarning
  from sktime.forecasting.base import ForecastingHorizon
  from sktime.utils.parallel import parallelize
  from sktime.utils.validation._dependencies import _check_soft_dependencies
  from sktime.utils.validation.forecasting import check_cv, check_scoring
label_desc: Use image node_id 1 for calling a global function with example usage: _check_strategy(strategy) without return types