[Azure clusters] how to specify one's own VNets?

I’m trying to deploy a cluster on Azure but it seems the VMs are network locked inside their own VNet created by ray. ray/azure-vm-template.json at master · ray-project/ray · GitHub

I have a use case where my VMs need to communicate with Hashicorp Vault on another VNet to get secrets to authenticate to other services. Why can’t I specify my own VNets with Azure Clusters?