/**
 * Replaces immediately-closing tags with self-closing tags, e.g replaces `<line></line>` with `<line/>`
 *
 * @param xml XML input
 */
export declare function addSelfClosingTags(xml: string): string;
/**
 * flattens an array of arrays
 *
 * @param arr the arrays to merge
 */
export declare function flatten<T>(arr: T[][]): T[];