/**
 * Recursively flattens a nested object into a flat object with dot-separated keys.
 *
 * @example
 * const input = { a: { b: 1, c: [2, 3] } };
 * flattenObject(input) // { 'a.b': 1, 'a.c.0': 2, 'a.c.1': 3 }
 *
 * @param obj The object to be flattened.
 * @param prefix Internal use for recursion.
 * @returns A flattened version of the input object.
 */
export declare function flattenObject(obj: any, prefix?: string): any;