def get_historic_trades(self, start, end, granularity, product_id='<STR_LIT>'):
params = {<EOL>'<STR_LIT:start>':self._format_iso_time(start),<EOL>'<STR_LIT:end>':self._format_iso_time(end),<EOL>'<STR_LIT>':granularity<EOL>}<EOL>return self._get('<STR_LIT>', product_id, '<STR_LIT>', params=params)<EOL>
`<https://docs.exchange.coinbase.com/#get-historic-rates>`_

        :param start: either datetime.datetime or str in ISO 8601
        :param end: either datetime.datetime or str in ISO 8601
        :pram int granularity: desired timeslice in seconds
        :returns: desired data