def parent_machine
      current = parent
      current = current.parent while current && !current.is_a?(VM)
      current
    end
def parent_machine
      current = parent
      current = current.parent while current && !current.is_a?(VM)
      current
    end
Gets the root machine of an AbstractModel by traversing a
 `parent` attribute until it reaches a type of {VM}.

 @return [VM]