/**
 * Defines a metadata on the target object.
 *
 * Replaces `Reflect.defineMetadata`.
 *
 * @param {string | symbol} key the key of the metadata
 * @param {any} value the value to be set in the metadata
 * @param {object} target the target on which the metadata should be set
 * @param {string | symbol} propertyName optional property name to add to the path on where value is set
 */
export declare function defineMetadata(key: string | symbol, value: any, target: object, propertyName?: string | symbol): void;
/**
 * Retrieves the metadata associated to `target` and `propertyName`.
 *
 * If not found, follows the prototype chain.
 *
 * Replaces `Reflect.getMedadata`.
 *
 * @param {string | symbol} key the key of the metadata
 * @param {object} target the target from which the metadata should be retrieved
 * @param {string | symbol} propertyName optional property name to add to the path on where value is retrieved
 * @returns {any} the value found, or `undefined` if not found
 */
export declare function getMetadata(key: string | symbol, target: object, propertyName?: string | symbol): any;