off(eventName, callback) {
    const handlers = this.eventHandlers[eventName] || [];
    if (callback) {
      const index = handlers.indexOf(callback);
      if (index === -1) {
        throw new Error(
          `Could not turn off specified event listener for "${eventName}": not found as a listener`,
        );
      }
      handlers.splice(index, 1);
    } else {
      delete this.eventHandlers[eventName];
    }
    return true;
  }
Turns off event listening for specific events
Calling without a callback will remove all listeners for the event
@param {string} eventName
@param {EventHandlerCallbackType} [callback]
@returns {true}