code: func (a AzureClient) CleanupSubnetIfExists(resourceGroup, virtualNetwork, name string) error {
  	return a.cleanupResourceIfExists(&subnetCleanup{
  		rg: resourceGroup, vnet: virtualNetwork, name: name,
  	})
  }
docs: // CleanupSubnetIfExists removes a subnet if there are no IP configurations
  // (through NICs) are attached to it. Note that this method is not safe for
  // multiple concurrent writers, in case of races, deployment of a machine could
  // fail or resource might not be cleaned up.