src/Metable/Hooks.php
public function __issetHook()
    {
        return function ($next, $isset, $args) {
            $key = $args->get('key');

            if (!$isset) {
                $isset = (bool) $this->hasMeta($key);
            }

            return $next($isset, $args);
        };
    }
public function __issetHook()
    {
        return function ($next, $isset, $args) {
            $key = $args->get('key');

            if (!$isset) {
                $isset = (bool) $this->hasMeta($key);
            }

            return $next($isset, $args);
        };
    }
Register hook on isset call.

@return \Closure