code: function _e2p(emitter, event, options) {
    let p = e2p(emitter, event, options);
  
    return p.then(() => {
      p.cancel();
      return p;
    })
    .catch(err => {
      p.cancel();
      throw err;
    });
  }
docs: /* allows to disconnect all those already
  unnecessary 'data', 'sent' and 'error' handlers.