input: def read_url(url: str) -> str:
      """ Given a URL, this function will read the contents from that URL and return the text if the response status code is 200. 
      Otherwise, it will return None.
      >>> read_url('https://www.example.com')
      'This is the content of the example.com website.'
      >>> read_url('https://www.nonexistentwebsite.com')
      None
      """
      
output:     import requests
      response = requests.get(url)
      if response.status_code == 200:
          return response.text
      else:
          return None