Only show unique edges in graphviz

Question

I have an input file with about ~5000 lines and 1 to 9 nodes per line.

Many edges are not unique and I would like to only show the unique ones.

A more simple example.

graph {
    a -- b
    a -- b
    a -- b
}

Yields

Is there a way to make the above graph yield something like

I know I could change the sample input to

graph {
    a -- b
}

But it would not be easy to do that for my real input.

Answer 1

There actually is a way: Use the strict keyword:

strict graph G {
    a -- b [label="First"];
    a -- b [label="Second"];
    a -- b [label="Third"];
}

Result:

Without strict, all three edges would be shown. Note that it only takes the first edge's attributes, contrary to what the documentation suggests.

Answer 2

Try strict:

strict graph {
    a -- b
    a -- b
    a -- b
}

This yields

and should work for any size of graph.