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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def shift(self, n, freq):
 """Shift the CFTimeIndex a multiple of the given frequency. See the documentation for :py:func:`~xarray.cftime_range` for a complete listing of valid frequency strings. Parameters n : int Periods to shift by freq : str or datetime.timedelta A frequency string or datetime.timedelta object to shift by Returns ------- CFTimeIndex See also -------- pandas.DatetimeIndex.shift Examples -------- CFTimeIndex([2000-01-31 00:00:00], dtype='object') CFTimeIndex([2000-02-29 00:00:00], dtype='object') """

        from .cftime_offsets import to_offset

        if not isinstance(n, int):
            raise TypeError("'n' must be an int, got {}.".format(n))
        if isinstance(freq, timedelta):
            return self + n * freq
        elif isinstance(freq, str):
            return self + n * to_offset(freq)
        else:
            raise TypeError(
                "'freq' must be of type "
                "str or datetime.timedelta, got {}.".format(freq))