So this is just multiplication of each term by exp(k*2*Pi*I*(degree of that term)). So the procedure (checked against your outputs) is below. So here k=0 would give sheet1 unchanged, k=1 would give sheet2, k=2 would give sheet3.
# find indeterminate
if nops(var)<>1 then
error "unable to determine variable"
# deg finds degree of a term
if generator::`+` then
generator*exp(k*2*Pi*I*deg(generator)) # if only one term
You could just pass the variable through as a second argument, which will be more efficient if you are doing it many times.