error(err) {
    const errs = Array.isArray(err) ? err : [err];
    if (this.ports.ports.error
      && (this.ports.ports.error.isAttached() || !this.ports.ports.error.isRequired())) {
      if (errs.length > 1) { this.sendIP('error', new IP('openBracket')); }
      errs.forEach((e) => { this.sendIP('error', e); });
      if (errs.length > 1) { this.sendIP('error', new IP('closeBracket')); }
    } else {
      errs.forEach((e) => { throw e; });
    }
  }
@param {Error|Error[]} err
@returns {void}