message: Fix documentation of guess_format_from_path_impl
diff: @@ -210,8 +210,9 @@ pub(crate) fn save_buffer_with_format_impl(
  }
  /// Guess format from a path.
  -/// If the path has no extension or it can not be convert to a `str` for comparison then this
  -/// method will simply return `None`.
  +///
  +/// Returns `PathError::NoExtension` if the path has no extension or returns a
  +/// `PathError::UnknownExtension` containing the extension if it can not be convert to a `str`.
  pub(crate) fn guess_format_from_path_impl(path: &Path) -> Result<ImageFormat, PathError> {
  let exact_ext = path.extension();
  