docs: def get_readme(self, ref=github.GithubObject.NotSet):
          """
          :calls: `GET /repos/:owner/:repo/readme <http://developer.github.com/v3/repos/contents>`_
          :param ref: string
          :rtype: :class:`github.ContentFile.ContentFile`
          """
          assert ref is github.GithubObject.NotSet or isinstance(ref, (str, unicode)), ref
          url_parameters = dict()
          if ref is not github.GithubObject.NotSet:
              url_parameters["ref"] = ref
          headers, data = self._requester.requestJsonAndCheck(
              "GET",
              self.url + "/readme",
              parameters=url_parameters
          )
          return github.ContentFile.ContentFile(self._requester, headers, data, completed=True)