public function get_upgrade( $upgrade_id = '', $step = 1 ) {
		$upgrade = $this->registry->get( $upgrade_id );

		if ( ! $upgrade ) {
			return false;
		}

		$class      = isset( $upgrade['class'] ) ? sanitize_text_field( $upgrade['class'] ) : '';
		$class_file = isset( $upgrade['file'] ) ? $upgrade['file'] : '';

		if ( ! class_exists( $class ) && ! empty( $class_file ) && file_exists( $class_file ) ) {
			require_once $class_file;
		} else {
			wp_send_json_error( array(
				'error' => sprintf( __( 'An invalid file path is registered for the %1$s batch process handler.', 'popup-maker' ), "<code>{$upgrade_id}</code>" ),
			) );
		}

		if ( empty( $class ) || ! class_exists( $class ) ) {
			wp_send_json_error( array(
				'error' => sprintf( __( '%1$s is an invalid handler for the %2$s batch process. Please try again.', 'popup-maker' ), "<code>{$class}</code>", "<code>{$upgrade_id}</code>" ),
			) );
		}

		/**
		 * @var PUM_Interface_Batch_Process|PUM_Interface_Batch_PrefetchProcess
		 */
		return new $class( $step );
	}