code: def _check_fh(
      fh: VALID_FORECASTING_HORIZON_TYPES,
  ) -> ForecastingHorizon:
      """Check and convert fh to format expected by CV splitters."""
      return check_fh(fh, enforce_relative=True)
  
file_path: sktime/sktime/split/base/_common.py
imports: from typing import Iterator, Optional, Tuple, Union
  import numpy
  import pandas
  from sktime.datatypes._utilities import get_window
  from sktime.forecasting.base import ForecastingHorizon
  from sktime.forecasting.base._fh import VALID_FORECASTING_HORIZON_TYPES
  from sktime.utils.validation import all_inputs_are_iloc_like, all_inputs_are_time_like, array_is_int, is_int
  from sktime.utils.validation.forecasting import check_fh
  from sktime.utils.validation.series import check_equal_time_index
label_desc: Use image node_id 1 for calling a global function with example usage: _check_fh(fh) and returns: check_fh