input: from typing import Optional
  
  def read_url(url: str) -> Optional[str]:
      """
      Reads the contents from a given URL. Returns the content as a string if the request is successful, otherwise returns None.
  
      >>> read_url("https://example.com")
      '<!doctype html>...'
      >>> read_url("https://nonexistenturlfortesting.com")
      None
      """
      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