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Method partially based on the excellent work described in:
 Qin, Xuebin, et al. "U2-Net: Going deeper with nested U-structure for salient object detection." Pattern Recognition 106 (2020): 107404
 Wang, Chenjie, et al. "U2-onet: A two-level nested octave u-structure network with a multi-scale attention mechanism for moving object segmentation." Remote Sensing 13.1 (2021): 60.