How to use the kfserving.V1alpha2CustomSpec function in kfserving

def customEndpointSpec(custom_model_spec):
    env = [client.V1EnvVar(name=i['name'], value=i['value']) for i in custom_model_spec['env']] if custom_model_spec.get('env', '') else None
    ports = [client.V1ContainerPort(container_port=int(custom_model_spec.get('port', '')))] if custom_model_spec.get('port', '') else None
    containerSpec = client.V1Container(
        name=custom_model_spec.get('name', 'custom-container'),
        image=custom_model_spec['image'],
        env=env,
        ports=ports,
        command=custom_model_spec.get('command', None),
        args=custom_model_spec.get('args', None),
        image_pull_policy=custom_model_spec.get('image_pull_policy', None),
        working_dir=custom_model_spec.get('working_dir', None)
    )
    return V1alpha2EndpointSpec(predictor=V1alpha2PredictorSpec(custom=V1alpha2CustomSpec(container=containerSpec)))