code: func GetStringPtr(d *schema.ResourceData, key string) *string {
  	v, e := d.GetOkExists(key)
  	if e {
  		return StringPtr(v.(string))
  	}
  	return nil
  }
docs: // GetStringPtr reads a ResourceData and returns an appropriate *string for the
  // state of the definition. nil is returned if it does not exist.