Jondeau 、Leon 等提出自回归条件方差—偏度—峰度模型(GARCHSK)，用于同时描述收益率二阶矩、三阶矩和四阶矩的时变特征。此文件为该模型代码。(Jondeau, Leon et al. Proposed an autoregressive conditional variance-skewness-kurtosis model (GARCHSK), which was used to describe the time-v