Is there a way we can classify between chest xray and not chest xray using keras?

Question

I'm new to deep learning and recently have been trying out some codes in Keras to develop a pneumonia classification program which uses a dataset that contains chest x-ray images. But before even using that program I want to add another layer of classification that will detect if the uploaded image is a chest Xray or not. If the uploaded image is a chest x-ray then only the pneumonia classification code will trigger or else it will show an error. As of now the code I am using for pneumonia classification accepts any kind of images, be it chest x-ray or an image of a dog or a cat and as such gives a prediction no matter what. So, I wanted to know if there is a way we can classify the uploaded image is a chest x-ray or an image of something else.