Name "spark" not found

Hi, when I following the guide and run the following command:

```
eksctl create iamserviceaccount \
--name spark \
--namespace spark \
--cluster spark-eks-best-practices \
--attach-policy-arn \
--approve --override-existing-serviceaccounts
```

it failed complaining the namespace spark is not found. I wonder if there are some other steps I'm missing -- for example, in some other online tutorials there are extra steps to install spark operators using helm:

```
helm repo add spark-operator https://googlecloudplatform.github.io/spark-on-k8s-operator
helm repo update
helm install spark-operator spark-operator/spark-operator --namespace spark-operator --create-namespace --set sparkJobNamespace=default
```

Thank you!