Optional types
types: Array<null | [number, number, number, number] | "constant" | "linear" | "quadIn" | "quadOut" | "quadInOut" | "cubicIn" | "cubicOut" | "cubicInOut" | "quartIn" | "quartOut" | "quartInOut" | "quintIn" | "quintOut" | "quintInOut" | "sineIn" | "sineOut" | "sineInOut" | "expoIn" | "expoOut" | "expoInOut" | "circIn" | "circOut" | "circInOut" | "elasticIn" | "elasticOut" | "elasticInOut" | "backIn" | "backOut" | "backInOut" | "bounceIn" | "bounceOut" | "bounceInOut" | "smooth" | "fade" | "quadOutIn" | "cubicOutIn" | "quartOutIn" | "quintOutIn" | "sineOutIn" | "expoOutIn" | "circOutIn" | "elasticOutIn" | "backOutIn" | "bounceOutIn"> = undefined
动画曲线。