/**
 * Prompts user for a single character input, displaying an optional message, and applies a provided callback to input.
 *
 * @param {string} [printedString=''] - Message displayed to user when prompting for input.
 * @param {function} [callback=(key) => key] - A callback function that processes user input before resolving promise. Defaults to an identity function that returns input unchanged.
 * @returns {Promise<string>} A promise that resolves to processed user input.
 */
export declare function inputch(printedString?: string, callback?: (key: string) => string): Promise<string>;