code: def attach_model(subscription, rgname, vmssvm_model, diskname, lun):
      '''Attach a data disk to a VMSS VM model'''
      disk_id = '/subscriptions/' + subscription + '/resourceGroups/' + rgname + \
          '/providers/Microsoft.Compute/disks/' + diskname
      disk_model = {'lun': lun, 'createOption': 'Attach', 'caching': 'None',
                    'managedDisk': {'storageAccountType': 'Standard_LRS', 'id': disk_id}}
      vmssvm_model['properties']['storageProfile']['dataDisks'].append(
          disk_model)
      return vmssvm_modef attach_model(subscription, rgname, vmssvm_model, diskname, lun):
      '''Attach a data disk to a VMSS VM model'''
      disk_id = '/subscriptions/' + subscription + '/resourceGroups/' + rgname + \
          '/providers/Microsoft.Compute/disks/' + diskname
      disk_model = {'lun': lun, 'createOption': 'Attach', 'caching': 'None',
                    'managedDisk': {'storageAccountType': 'Standard_LRS', 'id': disk_id}}
      vmssvm_model['properties']['storageProfile']['dataDisks'].append(
          disk_model)
      return vmssvm_model
docs: Attach a data disk to a VMSS VM model