import { HttpRequest } from '../../../../../types';
/**
 * Returns canonical headers.
 *
 * @param headers Headers from the request.
 * @returns Request headers that will be signed, and their values, separated by newline characters. Header names must
 * use lowercase characters, must appear in alphabetical order, and must be followed by a colon (:). For the values,
 * trim any leading or trailing spaces, convert sequential spaces to a single space, and separate the values
 * for a multi-value header using commas.
 *
 * @internal
 */
export declare const getCanonicalHeaders: (headers: HttpRequest['headers']) => string;