Parallel edges occur when there are two edges between a single pair of nodes.
IsParallelFree(arcSources, arcTargets, numNodes)
TRUE if the graph is parallel free, FALSE otherwise
Vector corresponding to the source nodes of a graph's edges
Vector corresponding to the destination nodes of a graph's edges
The number of nodes in the graph
See https://lemon.cs.elte.hu/pub/doc/1.3.1/a00616.html#gaa05e0683f90b69f31eb29fe7d09afde4 for more information.