export declare type Easing = 'linear' | 'sinusoid-in' | 'sinusoid-out' | 'sinusoid-in-out' | 'quadratic-in' | 'quadratic-out' | 'quadratic-in-out' | 'cubic-in' | 'cubic-out' | 'cubic-in-out' | 'quartic-in' | 'quartic-out' | 'quartic-in-out' | 'quintic-in' | 'quintic-out' | 'quintic-in-out' | 'exponential-in' | 'exponential-out' | 'exponential-in-out' | 'circular-in' | 'circular-out' | 'circular-in-out' | 'back-in' | 'back-out' | 'back-in-out' | string;