public function add_meta_box()
 {
     if (strstr($_SERVER['REQUEST_URI'], 'post-new.php')) {
         return false;
     }
     $existing = mailchimp_tools_get_existing_campaign_data_for_post(get_post($_GET['post']));
     if (!$existing) {
         return false;
     }
     parent::add_meta_box();
 }
 public function enqueue_assets()
 {
     parent::enqueue_assets();
     wp_register_script('mailchimp-tools-campaign-edit', MAILCHIMP_TOOLS_DIR_URI . '/assets/js/campaign-edit.js', array('mailchimp-tools-campaign-common'), MAILCHIMP_TOOLS_VER, true);
     $screen = get_current_screen();
     if ($screen->post_type == $this->post_type && $screen->base == 'post') {
         wp_enqueue_script('mailchimp-tools-campaign-edit');
     }
 }