“…Finally, in high‐order strategies, relation among more labels is considered. In addition to label correlation, there are several recently proposed topics in ML learning algorithms, including class‐imbalance (Li & Wang, n.d.; Spyromitros‐Xioufis, ; Zhang, Li, & Liu, ), label‐specific features (Huang, Li, Huang, & Wu, , ; Qiao, Zhang, Sun, & Liu, ; Xu et al, ; Zhang & LIFT, ), and data streams (Read, Bifet, Holmes, & Pfahringer, ; Song & Ye, ). Class‐imbalance problem happens when instances belonging to a certain label outnumber the instances that do not belong to it in the training set.…”