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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 readme(self):
 """Get the README for this repository. :returns: :class:`Contents <github3.repos.contents.Contents>` """

        url = self._build_url('readme', base_url=self._api)
        json = self._json(self._get(url), 200)
        return Contents(json, self) if json else None