You can find this exercise on page 164 of the book Synergistic Golf.
Exercise Type: PRE-ROUND WARMUP
Exercise Category: CHEST, FLEXIBILITY, SHOULDERS
Stand facing cart. Outstretch right arm and place open palm against cart support pole (or wall). Lift chest slightly and rotate 180 degrees to the left facing upper body and hips away from cart. Push palm into cart pole to promote stretch in front of shoulder and chest. Pause during exhale. Inhale release and stretch again. Repeat 3x each arm.