Can I update the pre-trained haar cascades classifiers stored in .xml files?

edit

I am performing Face Detection on a set of images using the pre-trained model with haar cascades. Would it be possible to update this existing model by retraining with a set of images from my own dataset? I aim to adapt the model to the specific characteristics of the faces that my dataset might have. Is this possible and does it make sense? If not, I guess it would make sense to create a custom classifier and then use e.g both of them for detecting the faces and combining them somehow. Sorry if the question is naive, I'm a beginner in Image Processing and OpenCV.