export declare type Listener = (...args: any) => void;
export declare class EventEmitter<T extends string> {
    callbacks: Record<string, any[]>;
    constructor();
    once(event: T, fn: (...args: any[]) => void): this;
    on(event: T, cb: (...args: any[]) => void): this;
    off(event?: T, fn?: (...args: any[]) => void): this;
    emit(event: T, ...args: any[]): this;
}
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