Error to load CameraRotation extension in Autodesk APS viewer

function loadModel(viewer, urn) {
function onDocumentLoadSuccess(doc) {
viewer.loadDocumentNode(doc, doc.getRoot().getDefaultGeometry());
viewer.loadExtension(‘CameraRotation’);
}
function onDocumentLoadFailure(viewerErrorCode, message) {
console.error(‘onDocumentLoadFailure() – errorCode:’ + viewerErrorCode);
console.error(message);
}
window.location.hash = urn;
Autodesk.Viewing.Document.load(‘urn:’ + urn, onDocumentLoadSuccess, onDocumentLoadFailure);
}