Method returns results from response of Yahoo YQL API. It should returns always python list.

def fetch_data(self):
        """Method returns results from response of Yahoo YQL API. It should returns always python list."""
        if relativedelta(self.end_date, self.start_date).years <= const.ONE_YEAR:
            data = self.request.send(self.symbol, self.start_date, self.end_date)
        else:
            data = self.fetch_chunk_data()

        return self.clean(data)