code: function getTurnPoint (turnPointInfo, network) {
    var key = turnPointInfo.lat + '_' + turnPointInfo.lon
    if (key in network.turnPoints) return network.turnPoints[key]
    var turnPoint = new TurnPoint(turnPointInfo, key)
    network.turnPoints[key] = turnPoint
    // network.addVertexPoint(turnPoint);
    return turnPoint
  }
docs: /* utility function for creating non-duplicative TurnPoints