anchor.diff:  
   module Pretty =
       /// <summary>
  +    ///     Prints a GraphViz label directive.
  +    /// </summary>
  +    /// <param name="labelCmd">
  +    ///     The pretty-printer command to use as the label.
  +    /// </param.
  +    /// <returns>
  +    ///     A pretty-printer command representing
  +    ///     [label = "<paramref name="labelCmd" />"].
  +    /// </returns>
  +    let printLabel labelCmd =
  +        [ String "label"
  +          String "="
  +          labelCmd |> ssurround "\"" "\"" ]
  +        |> hsep |> squared
  +    
  +    /// <summary>
       ///     Prints a node.
       /// </summary>
       /// <param name="id">
  
positive.code:     ///     A pretty-printer <c>Command</c> representing the node.
      /// </returns>
      let printNode id view =
          hsep [ sprintf "v%A" id |> String
                 squared (hsep [ String "label"
                                 String "="
                                 view |> printGView |> ssurround "\"" "\"" ])]
          |> withSemi
  
      /// <summary>
  
negative.code:     let printEdge { Pre = s; Post = t; Cmd = vf } =
          hsep [ s |> sprintf "v%A" |> String
                 String "->"
                 t |> sprintf "v%A" |> String
                 vf |> printVFunc |> printLabel ]
          |> withSemi
  
      /// <summary>
  