Learning sample with tf.sequential model


I succeed to learn images with mobilenet model.

But how to learn image with tf.sequential model ?

const _tf  = require('@tensorflow/tfjs');
const _tfnode = require('@tensorflow/tfjs-node');

/* Case With mobilenet */
const _mobilenet = require('@tensorflow-models/mobilenet');
const _knnClassifier = require('@tensorflow-models/knn-classifier');
_myModel	= await _mobilenet.load();
_myClassifier = _knnClassifier.create();
// learn img sample as classId
const activation = _myModel.infer( img, true);
_myClassifier.addExample( activation, classId);

/* Case with own-created tf.sequential */
_myModel = _tf.sequential();
// personalize model with layers...

let imageTensor = img
	.div( _tf.scalar(255.0))
const activation = _myModel.????

Best regards