igraph problem

Run this code

tree<-graph_from_literal(1-+2:3,3-+5,1-+4);
graph.bfs(tree,root=1, neimode="out",father=TRUE,order=TRUE,unreachable =
FALSE)

I do not understand why the father values will give NA 1 1 3 1 rather than NA
1 1 1 3

The reason I am doing this is to obtain the values(by vertex names) or some
index of each individual branch in tree. Does anyone have any ideas on how
to do this?

Yours sincerely,
Justin

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