export interface FormatBooleanOptions {
    true?: string;
    false?: string;
}
/**
 * Formats a boolean into a string.
 *
 * @param input The boolean to format.
 * @param options The options to use when formatting the boolean.
 * @returns The formatted boolean string, or `null` if the input is not a boolean.
 *
 * @example
 * ```typescript
 * formatBoolean(true, { true: "yes", false: "no" }); // "yes"
 * formatBoolean(false, { true: "yes", false: "no" }); // "no"
 * ```
 */
export declare function formatBoolean(input: unknown, options?: FormatBooleanOptions): string | null;