code: def _parse_expiry(response_data):
      
      expires_in = response_data.get('expires_in', None)
  
      if expires_in is not None:
          return _helpers.utcnow() + datetime.timedelta(
              seconds=expires_in)
      else:
          return None
docs: Parses the expiry field from a response into a datetime.
  
      Args:
          response_data (Mapping): The JSON-parsed response data.
  
      Returns:
          Optional[datetime]: The expiration or ``None`` if no expiration was
              specified.