def to(self, device) -> 'DataProto':
        """move the batch to device

        Args:
            device (torch.device, str): torch device

        Returns:
            DataProto: the current DataProto

        """
        if self.batch is not None:
            self.batch = self.batch.to(device)
        return self
move the batch to device

        Args:
            device (torch.device, str): torch device

        Returns:
            DataProto: the current DataProto

        
verl/protocol.py