WP Customizer setting argument

<?php

class Modular_Customizer_Output {

    public $output = array();

    public function __construct() {

        add_action( 'wp_enqueue_scripts', array( $this, 'my_styles_method' ) );
        add_filter( 'customize_dynamic_setting_args', array( $this, 'modular_add_output' ), 10, 2 );

    }

    public function modular_add_output( $settings_args, $setting_id ) {

        $output_css = '';
        $output     = $settings_args['output'];

        if ( ! empty( $output ) ) {
            $element  = $output[0]['element'];
            $property = $output[0]['property'];
            $value    = get_theme_mod( $setting_id );

            $output_css .= $element . '{ ' . $property . ': ' . $value . '}';

            $this->output = $output_css;
        }

    }

    function my_styles_method() {

        wp_add_inline_style( 'modular-style', $this->output );
    }

}

new Modular_Customizer_Output();