input: 
  def read_url(url: str) -> str:
      """ Read the contents from a given URL and return the text if the request is successful.
      If the request fails, return None.
      >>> read_url('https://www.example.com')
      '<!doctype html><html>...'
      >>> 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