How to add a filter for FlexSlider with Meta Slider

metaslider-filter.php

<?php //functions.php

add_filter('metaslider_flex_slider_parameters', 'metaslider_flex_params', 10, 3);

function metaslider_flex_params($options, $slider_id, $settings) 
{
        $options['after'][] = "onHomePageSlideChanged(slider);"; 
     
    return $options;
}

?>