/**
 * Returns a string representation of the input.
 *
 * Checks if the input is an object and if it has a toString() method, and if it does, it converts it to a string using that method.
 * If the input is not an object, null, undefined, NaN, or an empty string, it returns an empty string.
 * Otherwise, it returns the input converted to a string using the String() constructor.
 *
 * @param input
 * @returns string representation of the input
 */
export declare const toString: (input: any) => string;