create a
topology()
create b
topology()
a connect b(0), 1
topology()
a connect b(0), 0
topology()

forall delete_section()
create a,b,c,d
a connect b(0), 1
b connect c(0), 1
c connect d(0), 1
d connect b(0), 1
//above connected in loop so following produces an error message
topology()
