Adding the same edge to the vertex overwrites the previous one even if the other vertex is different

[fabianmurariu]

 * JGraphT version: 1.5.1
 * Java version (java -version)/platform:
openjdk version "17.0.4.1" 2022-08-12
OpenJDK Runtime Environment (Red_Hat-17.0.4.1.1-2.fc38) (build 17.0.4.1+1)
OpenJDK 64-Bit Server VM (Red_Hat-17.0.4.1.1-2.fc38) (build 17.0.4.1+1, mixed mode, sharing)  

Is there any graph kind supported by JGraphT that pass this test?

import scala.jdk.CollectionConverters._

class JGraphTSuite extends munit.FunSuite{
test("does not overwrite edges"){
    val g = new DefaultUndirectedGraph[Int, String](classOf[String])

    g.addVertex(1)
    g.addVertex(2)
    g.addVertex(3)
    g.addVertex(4)


    g.addEdge(2, 1, "one")
    g.addEdge(2, 3, "one")
    g.addEdge(2, 4, "one")

    val neighbours = Graphs.neighborSetOf(g, 2).asScala.toSet

    assertEquals(neighbours, Set(1, 3, 4)) // this fails
 }
}

[fabianmurariu]

I'll add this #437 as a reference since it was commented on 10 days ago

[jsichi]

https://jgrapht.org/guide/VertexAndEdgeTypes