code: def zPushLens(self, update=None, timeout=None):
          
          reply = None
          if update == 1:
              reply = self._sendDDEcommand('PushLens,1', timeout)
          elif update == 0 or update is None:
              reply = self._sendDDEcommand('PushLens,0', timeout)
          else:
              raise ValueError('Invalid value for flag')
          if reply:
              return int(reply)   # Note: Zemax returns -999 if push lens fails
          else:
              return -998
docs: Copy lens in the Zemax DDE server into LDE