code: def create_ref(self, ref, sha):
          
          json = None
          if ref and ref.count('/') >= 2 and sha:
              data = {'ref': ref, 'sha': sha}
              url = self._build_url('git', 'refs', base_url=self._api)
              json = self._json(self._post(url, data=data), 201)
          return Reference(json, self) if json else None
docs: Create a reference in this repository.
  
          :param str ref: (required), fully qualified name of the reference,
              e.g. ``refs/heads/master``. If it doesn't start with ``refs`` and
              contain at least two slashes, GitHub's API will reject it.
          :param str sha: (required), SHA1 value to set the reference to
          :returns: :class:`Reference <github3.git.Reference>` if successful
              else None