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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_assets(self, number=-1, etag=None):
 """Iterate over the assets available for this release. :param int number: (optional), Number of assets to return :param str etag: (optional), last ETag header sent :returns: generator of :class:`Asset <Asset>` objects """

        url = self._build_url('assets', base_url=self._api)
        return self._iter(number, url, Asset, etag=etag)