code: def get_signing_key(self, key_type):
          
          route_values = {}
          if key_type is not None:
              route_values['keyType'] = self._serialize.url('key_type', key_type, 'str')
          response = self._send(http_method='GET',
                                location_id='92ed5cf4-c38b-465a-9059-2f2fb7c624b5',
                                version='5.0-preview.1',
                                route_values=route_values)
          return self._deserialize('str', response)
docs: GetSigningKey.
          [Preview API]
          :param str key_type:
          :rtype: str