[Python] extend a pandas datetimeindex by 1 period

consider the DateTimeIndex dates

dates = pd.date_range('2016-01-29', periods=4, freq='BM')
dates

DatetimeIndex(['2016-01-29', '2016-02-29', '2016-03-31', '2016-04-29'],
dtype='datetime64[ns]', freq='BM')


I want to extend the index by one period at the frequency attached to the object.


I expect

pd.date_range('2016-01-29', periods=5, freq='BM')

DatetimeIndex(['2016-01-29', '2016-02-29', '2016-03-31', '2016-04-29',
'2016-05-31'],
dtype='datetime64[ns]', freq='BM')


I've tried

dates.append(dates[[-1]] + pd.offsets.BusinessMonthEnd())


However

• Not generalized to use frequency of dates
• I get a performance warning
  
  
  PerformanceWarning: Non-vectorized DateOffset being applied to Series or DatetimeIndex
  ​

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