/**
 * Constructable stylesheet cloning (adoptedStyleSheets).
 *
 * `adoptedStyleSheets` on a Document or ShadowRoot is the standard way Lit,
 * React and other frameworks inject component styles, but the sheets are not
 * part of the node tree — cloneNode never carries them. A shadow root that
 * relies on adopted sheets (and whose computed styles are not inlined per
 * element, i.e. copyStyles is false) would otherwise lose those rules in the
 * clone. The rules are re-materialised as a regular <style> element, which
 * also cascades last like the spec treats adopted sheets.
 */
/**
 * Serialize the CSS rules of the given sheets into one stylesheet string.
 * Sheets that cannot be read (e.g. detached) are skipped rather than failing
 * the render.
 */
export declare const serializeStyleSheetRules: (sheets: readonly CSSStyleSheet[]) => string;
/**
 * Build a <style> element carrying the rules of the given adopted sheets, or
 * null when there is nothing to clone. `styleDocument` must be the document
 * the clone lives in.
 */
export declare const createAdoptedStylesElement: (styleDocument: Document, sheets: readonly CSSStyleSheet[], nonce?: string) => HTMLStyleElement | null;