private function render_instances() {
		$data           = $this->get_data();
		$output         = null;
		$this->instance = 0;
		if ( ! empty( $data[ $this->slug ] ) ) {

			$data = array_filter( $data[ $this->slug ] );

			foreach ( (array) $data as $instance_id => $instance ) {
				$output .= $this->render_instance( $instance_id, $instance );
			}
		}

		return $output;
	}