import { Update } from '../types';
/**
    Updates fields in the document referred to by the specified DocumentReference. The update will fail if applied to a document that does not exist.

    @param reference — A reference to the document to update.
    
    @param data
    An object containing the fields and values with which to update the document. Fields can contain dots to reference nested fields within the document.
    
    @returns A Promise resolved once the data has been successfully written to the backend (note that it won't resolve while you're offline).
*/
export declare const updateDoc: Update;