code: def add_class(self, ioclass):
          
          current_ioclasses = self.ioclasses
          if ioclass.name in current_ioclasses.name:
              return
          current_ioclasses.append(ioclass)
          self.modify(new_ioclasses=current_ioclasses)
docs: Add one VNXIOClass instance to policy.
  
          .. note: due to the limitation of VNX, need to stop the policy first.