Sub-directory audio/image classification format plugins for wai.annotations.
- from-subdir-ac: reads audio files from sub-directories named after their class labels
- from-subdir-ic: reads images from sub-directories named after their class labels
- from-subdir-sc: reads spectra from sub-directories named after their class labels
- to-subdir-ac: writes audio files to sub-directories named after their class labels
- to-subdir-ic: writes images to sub-directories named after their class labels
- to-subdir-sc: writes spectra to sub-directories named after their class labels