“…In the second category, there are semi-supervised approaches, such as MixMatch [1], FixMatch [56] and FlexMatch [77], and others [1,41,48,52,69] that use pseudo-labeling or selflabeling, where unlabelled data is assigned pseudo-labels. Generative or teacher-student or ensemble models can also be listed among the semi-supervised approaches [12,16,23,33,38,49,53,55,59,64,65].…”