Selenium interaction with Chozen plugin in Codeception

WebHelper.php

<?php
namespace Codeception\Module;

// here you can define custom functions for WebGuy

/**
 * Class WebHelper
 * @package Codeception\Module
 */
class WebHelper extends \Codeception\Module
{
    /**
     * @param \WebGuy $I
     * @param $locator string XPath of li element which actually should be selected shown in the chozen list
     * @desc Chozen plugin does not support click trigger, only mousedown, that is why we need to refer to low-level
     * API of Selenium
     */
    function clickChzn(\WebGuy $I, $locator)
    {
        /**
         * @todo here we should check which module is currently used by Codeception
         * Maybe it is better to call an executeJs method which is supported by both Selenium and ZombieJS
         * like
         * $I->executeJS('$('.$locator.').mousedown()')
         * if jQuery or Zepto is used
         * didn't check with Prototype
         * Note, that in fact here XPath is passed, not a Sizzle-like selector
         * It is no reason to try to write this function on vanilla JS - Chozen won't work without jQuery/Prototype
         */
        $I->executeInSelenium(function (\Selenium\Browser $browser) use ($locator) {
            //active the whole chozen list
            //i assume that id of chozen is some_blablaId and id of chozen list item is some_blablaId_o_valueOfOption
            //@see AbstractChosen.prototype.result_add_option method
            $browser->mouseDown(preg_replace("/_[a-z]_[0-9]/", '', $locator));
            $browser->mouseUp($locator);
        });

    }
}