import type { CustomUserAttributeValue } from "../types";
/**
 * Sets a custom user attribute. This can be any key/value pair and is used to collect extra
 * information about the current user.
 *
 * @param key - The identifier of the custom attribute. Limited to 255 characters in length, cannot begin with
 *   a $, and can only contain alphanumeric characters and punctuation.
 * @param value - Can be numeric, boolean, a Date object, a string, or an array of strings. Strings are limited to
 *   255 characters in length, cannot begin with a $ and cannot contain new lines, tabs or double quotes.
 *   It can only include alphanumeric characters and other punctuation.
 *   Passing a null value will remove this custom attribute from the user.
 * @param merge - Whether the value should be merged with the existing value on the backend. If `false` (default), any existing
 *   attribute will be overwritten. If `true`, existing objects and arrays of objects will be merged. To update an array of objects,
 *   follow the guidelines in our
 *   [public docs](https://www.braze.com/docs/user_guide/data_and_analytics/custom_data/custom_attributes/array_of_objects/#usage-examples).
 *
 * @returns Resolves to a boolean that indicates whether the attribute was successfully enqueued. Resolves to undefined
 *   if the SDK is not initialized.
 */
export declare function setCustomUserAttribute(key: string, value: CustomUserAttributeValue, merge?: boolean): Promise<boolean | undefined>;