import { Expression } from '@tsdi/activities';
import { ITransform } from '../ITransform';
import { NodeActivityContext } from '../NodeActivityContext';
import { TransformActivity } from './TransformActivity';
export declare class StreamActivity extends TransformActivity {
    protected pipes: Expression<ITransform>[];
    execute(ctx: NodeActivityContext): Promise<ITransform>;
    /**
     * stream pipe transform.
     *
     * @protected
     * @param {NodeActivityContext} ctx
     * @param {ITransform} stream
     * @param {...Expression<ITransform>[]} pipes
     * @returns {Promise<ITransform>}
     * @memberof StreamActivity
     */
    protected pipeStreams(ctx: NodeActivityContext, stream: ITransform, ...pipes: Expression<ITransform>[]): Promise<ITransform>;
    static ρAnn(): any;
}