/**
 * Checks if the value is a string
 * @param value - The value to check
 */
export declare function isString(value: any): boolean;
/**
 * Checks if the value is an object
 * @param value - The value to check
 */
export declare function isObject(value: any): boolean;
/**
 * Checks if a MessageAttribute is valid
 * @param messageAttribute - The MessageAttribute to check
 */
export declare function isMessageAttributeValid(messageAttribute: any): boolean;