/**
 * Unified gRPC metadata class.
 */
export declare class Metadata {
    private data;
    /**
     * Creates a metadata object from a plain JavaScript object.
     * @param object Key-value object.
     * @returns A Metadata instance with the same key value pairs.
     */
    static fromObject(object: Record<string, string>): Metadata;
    /**
     * Converts this metadata instance into a plain JavaScript object.
     * @returns Object containing key value pairs.
     */
    toObject(): Record<string, string>;
    /**
     * Retrieves a string value from this metadata map.
     * @param key Key of the key value pair.
     * @returns The value.
     */
    get(key: string): string | undefined;
    /**
     * Sets a key value pair of the metadata map.
     * @param key Key of the key value pair.
     * @param value New value to insert.
     */
    set(key: string, value: string): void;
    /**
     * Sets a key value pair of the metadata map.
     * @param key Key of the key value pair.
     * @returns `true` if an element in the Map object existed and has been
     * removed, or `false` if the element does not exist.
     */
    delete(key: string): boolean;
}