export declare function isMaybeString(mixed: any): mixed is null | undefined | (string);
export declare function isMaybeMinLength(mixed: any, min: number): mixed is null | undefined | (string);
export declare function isMaybeMaxLength(mixed: any, max: number): mixed is null | undefined | (string);
export declare function isMaybeLength(mixed: any, args: {
    min?: number;
    max?: number;
}): mixed is null | undefined | (string);
export declare function isMaybeNonEmpty(mixed: any): mixed is null | undefined | (string);
export declare function isMaybeContains(mixed: any, x: string): mixed is null | undefined | (string);
export declare function isMaybeNoDuplicate(mixed: any): mixed is null | undefined | (string);
export declare function isMaybeNotAllWhitespace(mixed: any): mixed is null | undefined | (string);
export declare function isMaybeNonEmptyAndNotAllWhitespace(mixed: any): mixed is null | undefined | (string);
export declare function isMaybeMatch(mixed: any, regex: RegExp): mixed is null | undefined | (string);
export declare function isMaybeEmail(mixed: any): mixed is null | undefined | (string);
export declare function isMaybeNotOneOf<T extends string>(mixed: any, arr: T[]): mixed is null | undefined | (string);
export declare function isMaybeBase64(mixed: any): mixed is null | undefined | (string);
export declare function isMaybeJson(mixed: any): mixed is null | undefined | (string);