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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 postings(self, quarter, stats_counter=None):
 """Yield job postings in common schema format Args: quarter (str) The quarter, in format '2015Q1' stats_counter (object, optional) A counter that can track both input and output documents using a 'track' method. """

        logging.info('Finding postings for %s', quarter)
        for posting in self._iter_postings(quarter):
            transformed = self._transform(posting)
            transformed['id'] = '{}_{}'.format(
                self.partner_id,
                self._id(posting)
            )
            if stats_counter:
                stats_counter.track(
                    input_document=posting,
                    output_document=transformed
                )
            yield transformed