'Creates a test unregistering instances from load balancer.
Returns:
st.OperationContract'

def deregister_load_balancer_instances(self):

    payload = self.agent.type_to_payload('deregisterInstancesFromGoogleLoadBalancerDescription', {'loadBalancerNames': [self.__use_lb_name], 'instanceIds': self.use_instance_names[:2], 'region': self.bindings['TEST_GCE_REGION'], 'credentials': self.bindings['SPINNAKER_GOOGLE_ACCOUNT']})
    builder = gcp.GcpContractBuilder(self.gcp_observer)
    builder.new_clause_builder('Instances    not    in    Target    Pool', retryable_for_secs=30).list_resource('targetPools', region=self.bindings['TEST_GCE_REGION']).EXPECT(ov_factory.value_list_excludes(jp.DICT_MATCHES({'name': jp.STR_SUBSTR(self.__use_lb_tp_name), 'instances': jp.LIST_MATCHES([jp.STR_SUBSTR(self.use_instance_names[0]), jp.STR_SUBSTR(self.use_instance_names[1])])})))
    return st.OperationContract(self.new_post_operation(title='deregister_load_balancer_instances', data=payload, path='ops'), contract=builder.build())
