In the Gypsy Rhythm book, the picking pattern for the la pompe is notated as a short upstroke (the "grace" note) followed by downstroke (the main beat). However, in this Denis Chang's lesson:
it seems as though he's playing a downstroke for the "grace" note and then an upstroke for the main beat.
I then watched Django's on youtube j'attendrai video:
carefully to see if I can see the pattern that Joseph Reinhardt (Django's brother and accompanist) played. It seems as though he was playing the pattern that Denis Chang was playing. (not 100% sure) When I watched Nous'che from the Rosenberg Trio play the rhythm, it might have been the pattern from Horowitz's book Gypsy Rhythm (but again, I couldn't tell for sure).
For me, it was easier to keep the grace note very short using the pattern in Denis' video than that from the book. Is this just a different style or is one style more correct than the other?