<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def add_class(self, ioclass):
 """Add one VNXIOClass instance to policy. .. note: due to the limitation of VNX, need to stop the policy first. """

        current_ioclasses = self.ioclasses
        if ioclass.name in current_ioclasses.name:
            return
        current_ioclasses.append(ioclass)
        self.modify(new_ioclasses=current_ioclasses)