code: def create_dummy_datestamps(
      df,
      freq="S",
      startyear=1970,
      startmonth=1,
      startday=1,
      starthour=0,
      startminute=0,
      startsecond=0,
  ):
      """
      Helper function to create a dummy series of datestamps for equidistant data without ds.
      Parameters
      ----------
          df : pd.DataFrame
              dataframe with column 'y' and without column 'ds'
          freq : str
              Frequency of data recording, any valid frequency for pd.date_range, such as ``D`` or ``M``
          startyear, startmonth, startday, starthour, startminute, startsecond : int
              Defines the first datestamp
      Returns
      -------
          pd.DataFrame
              dataframe with dummy equidistant datestamps
  
      Examples
      --------
      Adding dummy datestamps to a dataframe without datestamps.
      To prepare the dataframe for training, import df_utils and insert your preferred dates.
          >>> from neuralprophet import df_utils
          >>> df_drop = df.drop("ds", axis=1)
          >>> df_dummy = df_utils.create_dummy_datestamps(
          >>> df_drop, freq="S", startyear=1970, startmonth=1, startday=1, starthour=0, startminute=0, startsecond=0
          >>> )
      """
      if "ds" in df:
          raise ValueError("Column 'ds' in df detected.")
      log.info(f"Dummy equidistant datestamps added. Frequency={freq}.")
      df_length = len(df)
      startdate = pd.Timestamp(
          year=startyear,
          month=startmonth,
          day=startday,
          hour=starthour,
          minute=startminute,
          second=startsecond,
      )
      datestamps = pd.date_range(
          startdate, periods=df_length, freq=freq
      )
      df_dummy = pd.DataFrame({"ds": datestamps, "y": df["y"]})
      return df_dummy
  
imports: from __future__ import annotations
  import logging
  import math
  from collections import OrderedDict
  from dataclasses import dataclass
  from typing import TYPE_CHECKING, List, Optional, Tuple
  import numpy
  import pandas
label_desc: Use image node_id 23 for calling a global function with example usage: create_dummy_datestamps(df, freq, startyear, startmonth, startday, starthour, startminute, startsecond) and returns: df_dummy