code: async def cas(self, value: Any, **kwargs) -> bool:
          
          success = await self.client.set(self.key, value, _cas_token=self._token, **kwargs)
          if not success:
              raise OptimisticLockError("Value has changed since the lock started")
          return True
docs: Checks and sets the specified value for the locked key. If the value has changed
          since the lock was created, it will raise an :class:`aiocache.lock.OptimisticLockError`
          exception.
  
          :raises: :class:`aiocache.lock.OptimisticLockError`