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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 iter_releases(self, number=-1, etag=None):
 """Iterates over releases for this repository. :param int number: (optional), number of refs to return. Default: -1 returns all available refs :param str etag: (optional), ETag from a previous request to the same endpoint :returns: generator of :class:`Release <github3.repos.release.Release>`\ s """

        url = self._build_url('releases', base_url=self._api)
        iterator = self._iter(int(number), url, Release, etag=etag)
        iterator.headers.update(Release.CUSTOM_HEADERS)
        return iterator