input: from typing import Optional
  
  def read_url(url: str) -> Optional[str]:
      """ Reads the contents from a given URL and returns the content as a string if the request is successful.
      If the request fails, it returns None.
      
      >>> read_url('https://www.example.com')
      'Example Domain\\n\\nExample Domain...'
      >>> read_url('https://nonexistent.example.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