code: function buildGraph(db, callback) {
  
    // Check cache for graph
    let cacheKey = db.id + "-graph";
    let cache = cache_graph.get(cacheKey);
    if ( cache !== null ) {
      return callback(null, cache);
    }
  
    // Build Graph
    let graph = new Graph();
  
    // Add the Vertices
    _addGraphVertices(db, graph, function(err, graph) {
  
      // Database Query Error
      if ( err ) {
        return callback(err);
      }
  
      // Add Graph Edges
      _addGraphEdges(db, graph, function(err, graph) {
  
        // Database Query Error
        if ( err ) {
          return callback(err);
        }
  
        // Return the finished graph
        cache_graph.put(cacheKey, graph);
        return callback(null, graph);
  
      });
  
    });
  
  }
docs: Build the entire Agency Line Graph
  @param {RightTrackDB} db The Right Track DB to query
  @param {function} callback Callback function
  @param {Error} callback.err Database Query Error
  @param {Graph} [callback.graph] Agency Graph
  @see {@link https://www.npmjs.com/package/graph.js|graph.js package}