WordPress plugin extending CMB2 metaboxes

index.php

<?php
/*
Plugin Name: NDM metaboxes
Description: portfolio metaboxes for NDM
Version: 0.11
Author: Alex Bachuk
Author URI: http://alexbachuk.com
License: GPL2
*/
?>
<?php 
add_action( 'admin_init', 'child_plugin_has_parent_plugin' );
function child_plugin_has_parent_plugin() {
    if ( is_admin() && current_user_can( 'activate_plugins' ) &&  !is_plugin_active( 'cmb2/init.php' ) ) {
        add_action( 'admin_notices', 'child_plugin_notice' );

        deactivate_plugins( plugin_basename( __FILE__ ) ); 

        if ( isset( $_GET['activate'] ) ) {
            unset( $_GET['activate'] );
        }
    }
}

function child_plugin_notice(){
    ?><div class="error"><p>Sorry, but NDM metaboxes requires the CMB2 plugin to be installed and active.</p></div><?php
}


include( plugin_dir_path( __FILE__ ) . 'post-metabox.php');