generate graph coverage for the following source code

namespace Opencart\Catalog\Model\Account;

class Activity extends \Opencart\System\Engine\Model {

public function addActivity(string $key, array $data): void {

if (isset($data['customer_id'])) {

$customer_id = $data['customer_id'];

} else {

$customer_id = 0;

}

$this->db->query("INSERT INTO `" . DB_PREFIX . "customer_activity` SET `customer_id` = '" . (int)$customer_id . "', `key` = '" . $this->db->escape($key) . "', `data` = '" . $this->db->escape(json_encode($data)) . "', `ip` = '" . $this->db->escape($this->request->server['REMOTE_ADDR']) . "', `date_added` = NOW()");

}

}