code: def _check_calendar(calendar: Dict[date, str]):
      """Check calendar param.
  
      Parameters
      ----------
      calendar : Dict[date, str]
          Dictionary with keys being holiday dates and values being
          holiday names.
  
      """
      for dte, name in calendar.items():
          if not (isinstance(dte, date) and isinstance(name, str)):
              raise ValueError(
                  "`calendar` must be a dictionary, with keys being date "
                  "and value being name of holiday."
              )
  
file_path: sktime/sktime/transformations/series/holiday/_holidayfeats.py
imports: import datetime
  from collections import defaultdict
  from datetime import date
  from typing import Dict
  import numpy
  import pandas
  from sktime.transformations.base import BaseTransformer
  from sktime.utils.validation._dependencies import _check_soft_dependencies
label_desc: Use image node_id 4 for calling a global function with example usage: _check_calendar(calendar) without return types