“…To this end, researchers have designed different unsupervised losses on target data for learning a well-performed model in target domain [27,34,35,68,72,75,47,77,5,8]. The existing unsupervised losses can be broadly classified into three categories: 1) adversarial loss that enforces source-like target representations in the feature, output or latent space [27,45,75,47,72,9,91,61,64,77,73,40,33,17,87,30]; 2) image translation loss that translates source images to have target-like styles and appearance [26,68,10,41,90,28,84,32]; and 3) self-training loss that re-trains networks iteratively with confidently pseudo-labelled target samples [96,95,66,92,41,16,31].…”