PresetLinearEasingKey: `${
    | `power${
        | "1"
        | "2"
        | "3"
        | "4"}`
    | "quad"
    | "expo"
    | "circ"
    | "sine"
    | "back"
    | "elastic"
    | "bounce"}-${"in" | "out" | "in-out"}`

Custom preset easing strings.

const str1: PresetLinearEasingKey = 'power2-in';
const str2: PresetLinearEasingKey = 'expo-in-out';
const str3: PresetLinearEasingKey = 'expo'; // INVALID