code: function _addGraphEdges(db, graph, callback) {
  
    // Counters
    let done = 0;
    let count = graph.vertexCount();
  
    // Loop through each Vertex in the Graph
    for ( let [stopId, stop] of graph ) {
  
      // Get the Edges for the Vertex
      _getStopEdges(db, stopId, function(err, edges) {
  
        // Database Query Error
        if ( err ) {
          return callback(err);
        }
  
        // Add each edge to the Graph
        for ( let i = 0; i < edges.length; i++ ) {
          graph.ensureEdge(stopId, edges[i]);
          graph.ensureEdge(edges[i], stopId);
        }
  
        // Finish the Vertex
        _finish();
  
      });
  
    }
  
    // Keep track of finished vertices
    function _finish() {
      done++;
      if ( done === count ) {
        return callback(null, graph);
      }
    }
  
  }
docs: Add edges to each Vertex in the Graph
  @param {RightTrackDB} db The Right Track DB to query
  @param {Graph} graph The Graph to add edges to
  @param {function} callback Callback function(err, graph)
  @private