/**
 * @license
 * Copyright 2020 Google LLC
 * SPDX-License-Identifier: BSD-3-Clause
 */
/**
 * Query the given parent element for a descendent with the given tag name and
 * return it, or throw if none or more than one are found.
 */
export declare function getOneElementByTagNameOrThrow(parent: Document | Element, tagName: string): Element;
/**
 * Return an attribute value from the given element, or throw if there is no
 * such attribute or it is the empty string.
 */
export declare function getNonEmptyAttributeOrThrow(element: Element, attributeName: string): string;