input: def read_url(url: str) -> str:
      """ Reads the contents from a given URL and returns the content as a string.
      If the request is not successful, it returns None.
      >>> read_url('https://httpbin.org/status/404')
      None
      >>> read_url('https://httpbin.org/get')
      {'args': {}, 'headers': {'Accept': '*/*', 'Accept-Encoding': 'gzip, deflate', 'Host': 'httpbin.org', 'User-Agent': 'python-requests/2.25.1'}, 'origin': '123.456.789.012', 'url': 'https://httpbin.org/get'}
      """
      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