/**
 * Validation types.
 */
export declare class ValidationTypes {
    static CUSTOM_VALIDATION: string;
    static NESTED_VALIDATION: string;
    static PROMISE_VALIDATION: string;
    static CONDITIONAL_VALIDATION: string;
    static WHITELIST: string;
    static IS_DEFINED: string;
    /**
     * Checks if validation type is valid.
     */
    static isValid(type: string): boolean;
}