Flask Load New Page After Streaming Data

I have simple Flask App that takes a CSV upload, makes some changes, and streams the results back to the user's download folder as CSV.

HTML Form

<form action =  method = "POST" enctype = "multipart/form-data">
    <label>CSV file</label><br>
    <input type = "file" name = "input_file" required></input><br><br>
    <!-- some other inputs -->
    <div id = "submit_btn_container">
        <input id="submit_btn" onclick = "this.form.submit(); this.disabled = true; this.value = 'Processing';" type = "submit"></input>
    </div>
</form>

PYTHON

from flask import Flask, request, Response, redirect, flash, render_template
from io import BytesIO
import pandas as pd

@app.route('/uploader', methods = ['POST'])
def uploadFile():
    uploaded_file = request.files['input_file']
    data_df = pd.read_csv(BytesIO(uploaded_file.read()))
    # do stuff
    
    # stream the pandas df as a csv to the user download folder
    return Response(data_df.to_csv(index = False),
                            mimetype = "text/csv",
                            headers = {"Content-Disposition": "attachment; filename=result.csv"})

This works great and I see the file in my downloads folder.

However, I'd like to display "Download Complete" page after it finishes.

How can I do this? Normally I use return redirect("some_url") to change pages.

from Flask Load New Page After Streaming Data