code: def stat(filename, retry_params=None, _account_id=None):
    
    common.validate_file_path(filename)
    api = storage_api._get_storage_api(retry_params=retry_params,
                                       account_id=_account_id)
    status, headers, content = api.head_object(
        api_utils._quote_filename(filename))
    errors.check_status(status, [200], filename, resp_headers=headers,
                        body=content)
    file_stat = common.GCSFileStat(
        filename=filename,
        st_size=common.get_stored_content_length(headers),
        st_ctime=common.http_time_to_posix(headers.get('last-modified')),
        etag=headers.get('etag'),
        content_type=headers.get('content-type'),
        metadata=common.get_metadata(headers))
  
    return file_stat
docs: Get GCSFileStat of a Google Cloud storage file.
  
    Args:
      filename: A Google Cloud Storage filename of form '/bucket/filename'.
      retry_params: An api_utils.RetryParams for this call to GCS. If None,
        the default one is used.
      _account_id: Internal-use only.
  
    Returns:
      a GCSFileStat object containing info about this file.
  
    Raises:
      errors.AuthorizationError: if authorization failed.
      errors.NotFoundError: if an object that's expected to exist doesn't.