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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 asset(self, id):
 """Returns a single Asset. :param int id: (required), id of the asset :returns: :class:`Asset <github3.repos.release.Asset>` """

        data = None
        if int(id) > 0:
            url = self._build_url('releases', 'assets', str(id),
                                  base_url=self._api)
            data = self._json(self._get(url, headers=Release.CUSTOM_HEADERS),
                              200)
        return Asset(data, self) if data else None