close(id) {
    if (id) {
      return this._removeLogger(id);
    }

    this.loggers.forEach((val, key) => this._removeLogger(key));
  }
Closes a `Logger` instance with the specified `id` if it exists.
If no `id` is supplied then all Loggers are closed.
@param {?string} id - The id of the Logger instance to close.
@returns {undefined}