input: 
  import requests
  
  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.nonexistentwebsite.com')
      None
      """
      r = requests.get(url)
      if r.status_code == 200:
          return r.text
      else:
          return None
  
output:     r = requests.get(url)
      if r.status_code == 200:
          return r.text
      else:
          return None