def delete_bigger(self):
        """ Delete all bigger duplicates.

        Only keeps the subset sharing the smallest size.
        """
        logger.info(
            "Deleting all mails strictly bigger than {} bytes...".format(
                self.smallest_size))
        # Select candidates for deletion.
        candidates = [
            mail for mail in self.pool
            if mail.size > self.smallest_size]
        if len(candidates) == self.size:
            logger.warning(
                "Skip deletion: all {} mails share the same size."
                "".format(self.size))
        logger.info(
            "{} candidates found for deletion.".format(len(candidates)))
        for mail in candidates:
            self.delete(mail)
Delete all bigger duplicates.

        Only keeps the subset sharing the smallest size.