anchor.diff:           |Some x -> x
            |None   -> failwithf "The vertex %O does not exist in the graph." v
   
  -    //
       //Label
       ///Returns Some label, if a label for the vertex v exists, else none.
       member this.TryGetLabel(v:'Vertex) :'Label option =        
  
positive.code: open System.Collections.Generic
  open FSharp.FGL //For our Graph method
  
  //  An immutable directed graph data structure efficient for large sparse
  //  graph representation where out-edge need to be enumerated only.
  //  Adaptation of https://github.com/YaccConstructor/QuickGraph.
  
  module internal Dictionary = 
  
  
negative.code:         this.TryGetOutEdges v
          |> Option.map (Array.length)
  
      ///Returns the weighted degree of the vertex v.
      member this.WeightedDegree(weightingF : LEdge<'Vertex,'Edge> [] -> 'T,v:'Vertex) :'T =
          match (Dictionary.tryGetValue v vertexOutEdges) with
  