def METHOD_NAME(self):
    self.connection.service_type = "compute"
    self.connection._ex_force_microversion = "2.67"
    headers = self.connection.add_default_headers({})
    self.assertEqual(headers["OpenStack-API-Version"], "compute 2.67")
    self.connection.service_type = "compute"
    self.connection._ex_force_microversion = "volume 2.67"
    headers = self.connection.add_default_headers({})
    self.assertNotIn("OpenStack-API-Version", headers)
    self.connection.service_type = "volume"
    self.connection._ex_force_microversion = "volume 2.67"
    headers = self.connection.add_default_headers({})
    self.assertEqual(headers["OpenStack-API-Version"], "volume 2.67")