input: 
  from typing import Optional
  
  def read_url(url: str) -> Optional[str]:
      """Read the contents from a given URL and return the content as a string if the request is successful.
      >>> read_url('https://www.example.com') is not None
      True
      >>> read_url('https://www.nonexistentwebsite.com') is not None
      False
      """
      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