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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 version(self):
 """Returns the version and revision of the gitlab server. Note that self.version and self.revision will be set on the gitlab object. Returns: tuple (str, str):
 The server version and server revision. ('unknown', 'unknwown') if the server doesn't perform as expected. """

        if self._server_version is None:
            try:
                data = self.http_get('/version')
                self._server_version = data['version']
                self._server_revision = data['revision']
            except Exception:
                self._server_version = self._server_revision = 'unknown'

        return self._server_version, self._server_revision