@ptrblck, the results for the print statements are shown in the image below. The tensor is the edge_index tuple with size “none”, “idx” prints “1” and edge_index[idx] prints a “none”.
With the posting of executable code to reproduce the issue, that will be a lot of code files to post because I’m running the main program which import a lot of different python files to execute including this message passing code. Probably I can post the full message passing code so that you can have a look.