public AdjacencyListGraph(bool isWeighted = false, bool isDirected = false)
 {
     _vertices  = new DictionaryOfCollection <int, Edge>();
     IsDirected = isDirected;
     IsWeighted = isWeighted;
 }
 public AdjacencyListGraph(bool isWeighted = false, bool isDirected = false)
 {
     _vertices = new DictionaryOfCollection<int, Edge>();
     IsDirected = isDirected;
     IsWeighted = isWeighted;
 }