“…As is well known, most nonlinear partial differential equations (PDEs) in mathematics and physics are integrable, including the Hirota equation [1], the nonlinear Schrödinger equation [2,3], the Gerdjikov-Ivanov equation [4], the Korteweg-de Vries equation [5,6], the Sasa-Satsuma equation [7], and so on. These nonlinear equations play an important role in various fields of nonlinear science such as water waves, nonlinear optics, and Bose-Einstein condensates.…”