↓ 6 callersFunctionLGraph_addUEdge* Add a new undirected edge to the graph, connecting id1 & id2.
*
* @graph The graph.
* @id1 ID of a node.
* @id2 ID of a node.
*
* @return 0 on
code/graph_algorithms/src/adjacency_lists_graph_representation/adjacency_lists_in_c/lgraph_struct.c:208