How to understand idrmg MPO constraction

Hi,ITensor:

I am learning the use of ITensor/iDMRG.Now l am courious about the MPO constraction in Heisenberg.h.l think l need to understand it as the example of other physics MPO.

l have read many question in [ITensor Support Q&A].However, some documents mentioned in the answers have disappeared in ITnesor C++. It seems difficult for me to understand how to manually construct the MPO of idmrg without the help of AutoMPO.

I sincerely hope that you can give me some corresponding guidance, which may be very important for me!!!After all, it is really difficult to learn without relevant documentation.

Hope you can understand my naive questions.Thanks for your helps!