How can i generate folded chain to simulate

[zhijs]

hi~ Gravelle, It is grateful that you created this handy tool to create chain for those who need, I want to create long chain to simulate, but if i use PEGgenerator to create chain, the simulation of this chain need big box, for example, if i created 1000 seg of chain, i need 210nm length of box to simulate, it is unsuitable to simulate, so i think that maybe i can create a folded chain like below image

so that i can use small box to simulate, therefore, I change the code of generator.py However, i got some errors in peg.itp when simulate, I don't why occured error, I would be thankful if you could give me some information about these errors.