def select(self, batch_keys=None, non_tensor_batch_keys=None, meta_info_keys=None, deepcopy=False) -> 'DataProto':
        """Select a subset of the DataProto via batch_keys and meta_info_keys

        Args:
            batch_keys (list, optional): a list of strings indicating the keys in batch to select
            meta_info_keys (list, optional): a list of keys indicating the meta info to select

        Returns:
            DataProto: the DataProto with the selected batch_keys and meta_info_keys
        """
        # TODO (zhangchi.usc1992) whether to copy
        if batch_keys is not None:
            batch_keys = tuple(batch_keys)
            sub_batch = self.batch.select(*batch_keys)
        else:
            sub_batch = self.batch

        if non_tensor_batch_keys is not None:
            non_tensor_batch = {key: val for key, val in self.non_tensor_batch.items() if key in non_tensor_batch_keys}
        else:
            non_tensor_batch = self.non_tensor_batch

        if deepcopy:
            non_tensor_batch = copy.deepcopy(non_tensor_batch)

        if meta_info_keys is not None:
            sub_meta_info = {key: val for key, val in self.meta_info.items() if key in meta_info_keys}
        else:
            sub_meta_info = self.meta_info

        if deepcopy:
            sub_meta_info = copy.deepcopy(sub_meta_info)

        return DataProto(batch=sub_batch, non_tensor_batch=non_tensor_batch, meta_info=sub_meta_info)
Select a subset of the DataProto via batch_keys and meta_info_keys

        Args:
            batch_keys (list, optional): a list of strings indicating the keys in batch to select
            meta_info_keys (list, optional): a list of keys indicating the meta info to select

        Returns:
            DataProto: the DataProto with the selected batch_keys and meta_info_keys
        
verl/protocol.py