How to represent a three-node energy system with one-way electricity transmission between the nodes?

[glatterf42]

Very sorry，I am establishing a three-node energy system, and I want to express the one-way electricity transmission between the nodes. I want Anhui to act as the electricity transmission center and transmit electricity to the other two nodes. However, in the final output results, Anhui becomes the electricity importing node, while the Shanghai node becomes the electricity exporting node. Where did I go wrong in expressing this?

Originally posted by @meng25meng in #798 (comment)

[glatterf42]

Thanks for the translation, much appreciated!
Now maybe @behnam-zakeri can jump in and explain in detail what went wrong, but I noticed one thing already: when setting up your destination exports (in cell 318), you are doing

for country in ["Shanghai", "Xinjiang"]:
    base_output.update(dict(technology="elec_exp", node_dest="hub", level="trade"))
    out = make_df("output", **base_output, node_loc=country)
    scen2.add_par("output", out)

So (if I understand the correctly), both "Shanghai" and "Xinjiang" will export electricity to a node called "hub", not to "Anhui". I don't think this is what you want to represent, since you only want to have three nodes in you system called "Anhui", "Shanghai", and "Xinjiang", right? So there should be no "hub".
And maybe to further clarify, how do you want to set up your system? Should "Anhui" both import from and export to "Shanghai" and "Xinjiang" or should it only export to them? Are "Shanghai" and "Xinjiang" supposed to trade with each other directly or only via "Anhui"?