Does anyone know how to convert a 3-level model with random-effects and random slopes from by -mixed- to by -gsem-

For example, the model by -mixed- is as below:

Code:
 mixed y x1 x2 x3 x4 c.x5#c.x4 || level2id: || level1id: x1 x2 x4, cov(un) reml
Could we test the same model with -gsem- ?