code: def _get_index_freq(data):
      freq = getattr(data.index, "freq", None)
      if freq is None:
          freq = getattr(data.index, "inferred_freq", None)
          if freq == "B":
              weekdays = np.unique(data.index.dayofweek)
              if (5 in weekdays) or (6 in weekdays):
                  freq = None
      return freq
  
imports: import functools
  from matplotlib import pylab
  import numpy
  from pandas._libs.tslibs.frequencies import FreqGroup, get_base_alias, get_freq, is_subperiod, is_superperiod
  from pandas._libs.tslibs.period import Period
  import pandas.compat
  from pandas.core.dtypes.generic import ABCDatetimeIndex, ABCPeriodIndex, ABCTimedeltaIndex
  from pandas.io.formats.printing import pprint_thing
  from pandas.plotting._converter import TimeSeries_DateFormatter, TimeSeries_DateLocator, TimeSeries_TimedeltaFormatter
  import pandas.tseries.frequencies
  from pandas.tseries.offsets import DateOffset
label_desc: Use image node_id 11 for calling a global function with example usage: _get_index_freq(data) and returns: freq