Unable to create Object

Hi,

i am writing a workflow, about checking some facts, so now i found the option "CheckAlarmsEnabled", result is true or false. But when i want to create an object, to enable the alarms for the hostsystem i get this error:

Info:

in_name_host = vchostsystem

test = new VcAlarmManager();
test.EnableAlarmActions(in_name_host,true);

 Unable to create object : VcAlarmManager : com.vmware.vmo.plugin.vi4.model.VimAlarmManager
[2017-01-30 16:07:42.213] [E] Workflow execution stack:
***
item: 'Alert/item7', state: 'failed', business state: 'null', exception: 'Unable to create object : VcAlarmManager :

Thanks for help