“…Financial time series data, such as stock returns, widely exists in our lives. Such data usually presents characteristics such as heteroscedasticity (Bollerslev, 1986; Engle, 1982), volatility clustering (Niu & Wang, 2013), large kurtosis (Alexander & Lazar, 2006), heavy‐tailed (Gong & Li, 2020), and asymmetry (Lisi, 2007; Zhang, Wang, & Yang, 2021). Among these characteristics the heteroscedasticity is the most typical one.…”