GAP 4.8.9 installation with standard packages -- copy to your CoCalc project to get it
# Line with C2-iso and a V4-point in between M := [ [1,2], [2,3] ]; C21 := Group( (1,2) ); C22 := Group( (3,4) ); V4 := Group( (1,2), (3,4) ); iso := rec( 1 := C21, 2 := V4, 3 := C22 ); mu := []; dim := 5; #