input: 
  import requests
  
  def read_url(url: str) -> str:
      """ Read the contents from a given URL
      >>> read_url('https://www.example.com')
      '<!doctype html>\n<html>\n<head>\n    <title>Example Domain</title> ...'
      >>> read_url('https://www.nonexistenturl.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