/**
 * Check if given is `CronStartOrBlank`.
 *
 * @category Predicates
 * @example
 * ```typescript
 * isCronStartOrBlank("?"); // true
 * isCronStartOrBlank("INVALID"); // false
 * ```
 * @param value Value to check.
 * @returns Returns `true` if is `CronStartOrBlank`, `false` otherwise.
 */
export declare const isCronStartOrBlank: (value: unknown) => value is "?";