input: 
  import requests
  
  def read_url(url: str) -> str:
      """ Reads the contents from a given URL and returns the text if the request is successful (status code 200).
      Returns None otherwise.
      
      >>> read_url('https://www.example.com')
      '<!doctype html>\n<html>\n<head>\n    <title>Example Domain</title>\n    ...'
      
      >>> read_url('https://www.nonexistent-website.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