export declare function isString(mixed: any): mixed is string;
export declare function isMinLength(mixed: any, min: number): mixed is string;
export declare function isMaxLength(mixed: any, max: number): mixed is string;
export declare function isLength(mixed: any, args: {
    min?: number;
    max?: number;
}): mixed is string;
export declare function isNonEmpty(mixed: any): mixed is string;
export declare function isContains(mixed: any, x: string): mixed is string;
export declare function isNoDuplicate(mixed: any): mixed is string;
export declare function isNotAllWhitespace(mixed: any): mixed is string;
export declare function isNonEmptyAndNotAllWhitespace(mixed: any): mixed is string;
export declare function isMatch(mixed: any, regex: RegExp): mixed is string;
export declare function isEmail(mixed: any): mixed is string;
export declare function isNotOneOf<T extends string>(mixed: any, arr: T[]): mixed is string;
export declare function isBase64(mixed: any): mixed is string;
export declare function isJson(mixed: any): mixed is string;