code: def get_dow_grouped_suffix(date: datetime.datetime) -> str:
      """Utility function to generate a suffix given an input ``date``.
  
      Parameters
      ----------
      date : `datetime.datetime`
          Input timestamp.
  
      Returns
      -------
      suffix : `str`
          The suffix string starting with "_".
      """
      if date.day_name() == "Saturday":
          return "_Sat"
      elif date.day_name() == "Sunday":
          return "_Sun"
      elif date.day_name() in ["Friday", "Monday"]:
          return "_Mon/Fri"
      else:
          return "_WD"
  
file_path: greykite/greykite/algo/common/holiday_utils.py
imports: import datetime
  from typing import Any
  from typing import Dict
  from typing import List
  from typing import Optional
  import pandas
  from pandas.tseries.frequencies import to_offset
  from greykite.algo.forecast.silverkite.forecast_simple_silverkite_helper import get_event_pred_cols
  from greykite.common.constants import EVENT_DF_DATE_COL
  from greykite.common.constants import EVENT_DF_LABEL_COL
  from greykite.common.constants import EVENT_PREFIX
  from greykite.common.constants import EVENT_SHIFTED_SUFFIX_AFTER
  from greykite.common.constants import EVENT_SHIFTED_SUFFIX_BEFORE
  from greykite.common.python_utils import split_offset_str
label_desc: Use image node_id 1 for calling a global function with example usage: get_dow_grouped_suffix(date) and returns: str, str, str, str