export abstract class Supervisor<N extends string, P = unknown, R = unknown> {
  private static instances_: Set<Supervisor<string, unknown, unknown>>;
  private static get instances(): typeof Supervisor.instances_ {
    return this.hasOwnProperty('instances_')
      ? this.instances_
      : this.instances_ = new Set();
  }
  constructor() {
    void (this.constructor as typeof Supervisor).instances.add(this);
  }
  public abstract call(name: N | ('' extends N ? undefined : never), param: P, timeout?: number): Promise<R>;
}