[NTG-context] Construct a matrice with Metafun and \MATRIX{}

Hi, I tried to use Metafun and \definemathmatrix [pmatrix] [matrix: parentheses] [simplecommand = MATRIX] to create two matrices, but that does not work. Thank you. http://image.noelshack.com/fichiers/2018/41/7/1539507927-matrice.jpg