Change the nodes to be filtered by targetLabel

[Jafeyyu]

Change the nodes to be filtered by targetLabel from PATH_START&PATH_START to PATH_START&PATH_END.

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[michael-simons]

Thanks a lot, @Jafeyyu As much as I would have liked to merge or cherry pick that into my branch with tests added, I cannot.

Of course I had that solution myself, but it turned out that we can simplify the path mapping by a magnitude without changing functionality. You will see in the solution to #2114.