Ionic doctor check command doesn't work any more

does any one have this problem while running ionic doctor check command?
doctor is not a valid task
it was working well 1 week ago

I didn’t know this command and it works on my computer

sorry it was cause of old version ionic even i don’t know how it was downgraded.not exactly downgraded there was 2 version of ionic installed. i uninstalled the old version and now works properly