The example on docs.rs states that the output of the last println! is supposed to be:

graph {
    0 [label="\"0\""]
    1 [label="\"0\""]
    2 [label="\"0\""]
    3 [label="\"0\""]
    1 -- 2
    3 -- 4
    2 -- 3
}

However, it actually is:

graph {
    0 [ label = "0" ]
    1 [ label = "0" ]
    2 [ label = "0" ]
    3 [ label = "0" ]
    4 [ label = "0" ]
    1 -- 2 [ ]
    3 -- 4 [ ]
    2 -- 3 [ ]
}

This highlights pretty well, one of the reasons why I find the example confusing. Using from_edges in the beginning starting with 1 as the lowest index creates a 0 node which does nothing. Hence I would suggest changing the example slightly and shift the indices of the nodes in the example.