Python networkx library help

Does anyone now how to modify "def dag_longest_path(G)" in networkx.github.io/documentation/networkx-1.10/_modules/networkx/algorithms/dag.html#dag_longest_path

to make it relative from a certain vertex I choose? I've been trying to code trace it for quite some time but I can't really seem to understand it, there are some functionalities like G.pred[node] which always come up with an empty set which doesnt make any sense.

bump

post more akarin

Longest path from a certain vertex to what?

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reject the for loop and instead only use the node you supply as a second argument?