/**
 * Environment available in external commands.
 * Stores which entries have changed so that only the changed values are copied back to
 * the WebWorker environment rather than all the entries.
 */
export declare class ExternalEnvironment extends Map<string, string> {
    delete(key: string): boolean;
    /**
     * Return object containing only those entries that have changed, or undefined if no
     * values have changed.
     * An entry with a string value has changed to that string.
     * An entry with an undefined value has been deleted.
     */
    get changed(): {
        [key: string]: string | undefined;
    } | undefined;
    set(key: string, value: string): this;
    private _changed?;
}