export declare function isBrowser(): boolean;
declare const converters: {
    readonly boolean: (value: string | undefined) => boolean | undefined;
    readonly string: (value: string | undefined) => string | undefined;
};
type Converters = typeof converters;
export declare function getOptionalEnv<EnvType extends keyof Converters = 'string'>(envName: string, envType?: EnvType): ReturnType<Converters[EnvType]> | undefined;
export {};