You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: mod.rs
    path of file: ./repos/LakeSoul/rust/lakesoul-io/src/default_column_stream
    
    the code of the file until where you have to start completion: // SPDX-FileCopyrightText: 2023 LakeSoul Contributors
//
// SPDX-License-Identifier: Apache-2.0

pub mod empty_schema_stream;

use futures::{Stream, StreamExt};
use std::collections::HashMap;
use std::fmt::{Debug, Formatter};
use std::pin::Pin;
use std::sync::Arc;
use std::task::{Context, Poll};

use arrow::datatypes::SchemaRef;
use arrow::record_batch::RecordBatch;

use datafusion::error::Result;
use datafusion::physical_plan::{RecordBatchStream, SendableRecordBatchStream};

use crate::transform::{transform_record_batch, transform_schema};

pub(crate) struct WrappedSendableRecordBatchStream {
    stream: SendableRecordBatchStream,
}

impl Debug for WrappedSendableRecordBatchStream {
    fn fmt(&self, f: &mut Formatter) -> std::fmt::Result {
        write!(f, "WrappedSendableRec
    
    fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
        loop {
            if self.cur_stream_idx >= self.inner_stream.len() {
                return Poll::Ready(None);
            }
            let idx = self.cur_stream_idx;
            let stream = &mut self.inner_stream[idx].stream;
            return match futures::ready!(stream.poll_next_unpin(cx)) {
                None => {
                    self.cur_stream_idx += 1;
                    continue;
                }
                Some(Err(e)) => Poll::Ready(Some(Err(e))),
                Some(Ok(batch)) => {
                    let batch = transform_record_batch(
                        self.schema(),
                        batch,
                        self.use_default,
                        self.default_column_value.clone(),
                    );
                    Poll::Ready(Some(batch))
                }
            };
        }
    }