GAP 4.8.9 installation with standard packages -- copy to your CoCalc project to get it
#g2 f3 % almost decomposable bravais-group 4 % generator 0 1 0 0 -1 1 0 0 0 0 0 -1 0 0 1 1 4 % generator 0 1 0 0 1 0 0 0 0 0 0 1 0 0 1 0 4 % invariant form 2 -1 0 0 -1 2 0 0 0 0 0 0 0 0 0 0 4 % invariant form 0 0 0 3 0 0 3 0 0 3 0 0 3 0 0 0 4 % invariant form 0 0 0 0 0 0 0 0 0 0 6 3 0 0 3 6 2^2 * 3^1 = 12 % order of the group