“…Typical research fields of DA, such as unsupervised domain adaptation (UDA) [60], [68], [29], [28], [34], [67], multisource domain adaptation (MSDA) [73], [39], [66], [69], [57], and multi-target domain adaptation (MTDA) [7], [32], [57], [14], [63], [13] suppose both the source and the target datasets are available for model training. For each new target domain, they have to re-collect target data and use it to repeat the training process, which is expensive, time-consuming, or even infeasible.…”