def get_files(self, is_dl_forced, files=None):
        """
        Given a set of files for this source, it will go fetch them, and
        set a default version by date.  If you need to set the version number
        by another method, then it can be set again.
        :param is_dl_forced - boolean
        :param files dict - override instance files dict
        :return: None
        """

        fstat = None
        if files is None:
            files = self.files
        for fname in files:
            LOG.info("Getting %s", fname)
            headers = None
            filesource = files[fname]
            if 'headers' in filesource:
                headers = filesource['headers']
            self.fetch_from_url(
                filesource['url'], '/'.join((self.rawdir, filesource['file'])),
                is_dl_forced, headers)
            # if the key 'clean' exists in the sources `files` dict
            # expose that instead of the longer url
            if 'clean' in filesource and filesource['clean'] is not None:
                self.dataset.setFileAccessUrl(filesource['clean'])
            else:
                self.dataset.setFileAccessUrl(filesource['url'])

            fstat = os.stat('/'.join((self.rawdir, filesource['file'])))

        # only keeping the date from the last file
        filedate = datetime.utcfromtimestamp(fstat[ST_CTIME]).strftime("%Y-%m-%d")

        # FIXME
        # change this so the date is attached only to each file, not the entire dataset
        self.dataset.set_date_issued(filedate)
Given a set of files for this source, it will go fetch them, and
        set a default version by date.  If you need to set the version number
        by another method, then it can be set again.
        :param is_dl_forced - boolean
        :param files dict - override instance files dict
        :return: None