/**
 * Returns a set of headers to use in an HTTP request, merging them with any existing headers in options.
 * @param {Record<string, string> | undefined} [existingHeaders] - Optional existing headers to merge with the tracing headers.
 * @param {string} [header] - The tracing header name to use.
 * @returns {Record<string, string> | undefined} The merged headers, or undefined if no tracing header is available.
 */
export function applyTraceHeaders(existingHeaders?: Record<string, string> | undefined, header?: string): Record<string, string> | undefined;
/**
 * Validates if a string conforms to the uuid structure
 * @param {string} str
 * @returns
 */
export function isValidUUID(str: string): boolean;