BrowserMob Proxy Not Returning Data

Hello I'm trying get a har file using the code below but it is not return any har data? Does anyone have clues on what might be going wrong?

from browsermobproxy import Server

server = Server("./bin/browsermob-proxy")

server.start()
proxy = server.create_proxy()

from selenium import webdriver
co = webdriver.ChromeOptions()
co.add_argument('--proxy-server={host}:{port}'.format(host='localhost', port=proxy.port))

driver = webdriver.Chrome(executable_path="chromedriver", chrome_options=co)

proxy.new_har('req',options={'captureHeaders': True,'captureContent':True})

driver.get(url)
proxy.har  # returns a HARenter code here