Data and Code for "Pseudo-linear Summation explains Neural Geometry of Multi-finger Movements in Human Premotor Cortex", Nishal P. Shah, Donald Avansino, Foram Kamdar, Claire Nicolas, Anastasia Kapitonava, Carlos Vargas-Irwin, Leigh R. Hochberg, Chethan Pandarinath, Krishna V Shenoy, Francis R Willett, Jaimie M. Henderson