/**
 * Backfills canonical kebab-case widget attributes from their legacy
 * snake_case spelling.
 *
 * For each canonical name (e.g. `article-id`), if it is absent or blank but the
 * snake_case form (`article_id`) carries a value, the value is copied onto the
 * canonical attribute. Lets a widget migrate its attribute naming without
 * breaking embeds that still use the old names. Mutates `element` in place.
 * @param {Element} element - The custom element to normalize.
 * @param {readonly string[]} canonicalNames - The canonical kebab-case attribute names.
 * @returns {void} Nothing.
 */
export declare const normalizeLegacyAttributes: (element: Element, canonicalNames: readonly string[]) => void;
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