/**
  * Returns single instance of the class
  *
  * @since 1.0.0
  */
 public static function get_instance()
 {
     if (is_null(self::$instance)) {
         self::$instance = new self();
     }
     return self::$instance;
 }
 /**
  * On plugin init check query vars for commands to import default tax rates
  */
 function check_import_actions()
 {
     if (!isset($_GET["install-tax-rates"])) {
         return;
     }
     if ("standard" == $_GET["install-tax-rates"]) {
         //  import standard tax rates
         YITH_Tax_Rates::get_instance()->install_standard_rates();
     } elseif ("reduced" == $_GET["install-tax-rates"]) {
         //  import reduced tax rates
     }
     wp_redirect(esc_url_raw(remove_query_arg("install-tax-rates")));
 }