export declare abstract class CollapsibleElement extends HTMLElement {
    arrowDown: Element;
    arrowUp: Element;
    triggerElement: HTMLElement;
    collapsibleElements: HTMLElement[];
    collapsed: boolean;
    toggleViaKeyboard(event: KeyboardEvent): void;
    toggle(): void;
    attributeChangedCallback(name: string): void;
    hideAll(): void;
    expandAll(): void;
    abstract get baseClass(): string;
}