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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 _validate_freq(self):
 """ Validate & return window frequency. """

        from pandas.tseries.frequencies import to_offset
        try:
            return to_offset(self.window)
        except (TypeError, ValueError):
            raise ValueError("passed window {0} is not "
                             "compatible with a datetimelike "
                             "index".format(self.window))