fetch/compression-dictionary/resources/echo-headers.py

import json

def main(request, response):
    response.headers.set(b"Access-Control-Allow-Origin", b"*")
    headers = {}
    for header in request.headers:
        key = header.decode('utf-8')
        value = request.headers.get(header).decode('utf-8')
        headers[key] = value
    return json.dumps(headers)