code: def maybe_convert_index(ax: Axes, data):
      # tsplot converts automatically, but don't want to convert index
      # over and over for DataFrames
      if isinstance(data.index, (ABCDatetimeIndex, ABCPeriodIndex)):
          freq: str | BaseOffset | None = data.index.freq
  
          if freq is None:
              # We only get here for DatetimeIndex
              data.index = cast("DatetimeIndex", data.index)
              freq = data.index.inferred_freq
              freq = to_offset(freq)
  
          if freq is None:
              freq = _get_ax_freq(ax)
  
          if freq is None:
              raise ValueError(
                  "Could not get frequency alias for plotting"
              )
  
          freq_str = _get_period_alias(freq)
  
          if isinstance(data.index, ABCDatetimeIndex):
              data = data.tz_localize(None).to_period(freq=freq_str)
          elif isinstance(data.index, ABCPeriodIndex):
              data.index = data.index.asfreq(freq=freq_str)
      return data
  
imports: from __future__ import annotations
  from datetime import timedelta
  import functools
  from typing import TYPE_CHECKING, cast
  import numpy
  from pandas._libs.tslibs import BaseOffset, Period, to_offset
  from pandas._libs.tslibs.dtypes import FreqGroup
  from pandas.core.dtypes.generic import ABCDatetimeIndex, ABCPeriodIndex, ABCTimedeltaIndex
  from pandas.io.formats.printing import pprint_thing
  from pandas.plotting._matplotlib.converter import TimeSeries_DateFormatter, TimeSeries_DateLocator, TimeSeries_TimedeltaFormatter
  from pandas.tseries.frequencies import get_period_alias, is_subperiod, is_superperiod
label_desc: Use image node_id 12 for calling a global function with example usage: maybe_convert_index(ax, data) and returns: data