Duplicated edges from Graph.edges(g, v) when v has a self-reference?

从 lib/graph.ex 约第 451 行开始，使用一条自引用边重现 Graph.edges(graph, metric_key)。将返回的边与 Graph.edges(graph) 进行比较，并检查 v_in 和 v_out 路径是如何组合和去重的。完成的标准是确定自引用的预期行为，并由回归测试覆盖。

Hi and first of all, thanks for maintaining this library. It has turned out to be essential to me since I started using it.

I'm a big fan of pattern matching over edges in the graph and it's a very intuitive way to write complicated case handling. However I just discovered that I'm getting duplicated edges when I am matching on, eg.

case graph |> Graph.edges(metric_key) do
    %{v1: ^metric_key, v2: ^metric_key} -> ...
    ... other cases
end

From a glance at the code, a possible cause could be if a self-referencing edge could be described by both v_in and v_out:
https://github.com/bitwalker/libgraph/blob/15ff0b9ba8c22a9dfec5bc04096fb7025e58f34b/lib/graph.ex#L451

But the description would have to differ, otherwise the MapSet would make it unique.. Do you think this is a correct cause and if so, is it an intended one?

I don't suppose there is any inherent disadvantage in just matching instead on all edges as such:

case graph |> Graph.edges() do
    %{v1: ^metric_key, v2: ^metric_key} -> ...
    ... other cases
    _ -> [] # not the stuff we're interested in
end |> List.flatten()

Looking at the code, it seems to be pretty much the same amount of work being done -- and in my situation, I always need to flat_map anyway in what I am doing.

However, someone else may be tripped up on it and have a situation where getting duplicates could cause confusion down the line.

Best regards,
Dennis