input: def read_url(url: str) -> str:
      """Reads the contents from a given URL and returns it as a string. If the request fails, it returns None.
      >>> read_url('https://www.example.com/')
      '<!doctype html>\\n<html>\\n<head>\\n<title>Example Domain</title>\\n...'
      >>> read_url('https://www.invalidurl.com/')
      None
      """
      import requests
      r = requests.get(url)
      if r.status_code == 200:
          return r.text
      else:
          return None
output:     import requests
      r = requests.get(url)
      if r.status_code == 200:
          return r.text
      else:
          return None