In applications such as facial image retrieval, given a sample image, a retrieval systemis supposed to return a set of images that are similar to the sample image. To improve retrieval accuracy, human intervention can be invited to manually tell the system,among the set of returned images, which ones are indeed related to the sample image. Discuss how the user response can be specifically used to improve theperformance of the retrieval system. (Hint: this is a question related to semi-supervised and/or reinforcement learning.)