To Camillo Bruni: I'm not using any slot image (I only looked over the paper). According to the Pharo book, 'pvt' should be implemented in the mainstream image.
To Marcus Denker: There are actually several methods in the image with the 'pvt' prefix. Please update the doc (Pharo book) to remove talking about 'pvt'. It would have saved me a little headache :)
