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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 get_filename(self, renew=False):
 """Get the filename of this content. If the file name doesn't already exist, we created it as {id}.{format}. """

        if self._fname is None or renew:
            self._fname = '%s.%s' % (self._id, self._format)
        return self._fname