Metabor\KeyValue\Composite::offsetExists PHP Method

    public function offsetExists($offset)
    {
        if ($this->container->count()) {
            $result = true;
            /* @var $keyValue \ArrayAccess */
            foreach ($this->container as $keyValue) {
                $result = $result && $keyValue->offsetExists($offset);
            }
            return $result;
        } else {
            return false;
        }
    }