public function filter(callable $condition)
    {
        $storage = [];

        foreach ($this->storage as $key => $value) {
            if ($condition($key, $value)) {
                $storage[$key] = $value;
            }
        }

        return new static($this->keyType, $this->valType, $storage);
    }
public function filter(callable $condition)
    {
        $storage = [];

        foreach ($this->storage as $key => $value) {
            if ($condition($key, $value)) {
                $storage[$key] = $value;
            }
        }

        return new static($this->keyType, $this->valType, $storage);
    }
{@inheritdoc}