protected function exists($key)
    {
        return isset($this->cache[$key]) && in_array($this->cache[$key]['state'], [self::STATE_ALIGNED, self::STATE_PENDING_WRITE]);
    }
protected function exists($key)
    {
        return isset($this->cache[$key]) && in_array($this->cache[$key]['state'], [self::STATE_ALIGNED, self::STATE_PENDING_WRITE]);
    }
protected function exists ( $ key ) { return isset ( $ this -> cache [ $ key ] ) && in_array ( $ this -> cache [ $ key ] [ 'state' ] , [ self :: STATE_ALIGNED , self :: STATE_PENDING_WRITE ] ) ; }
Checks if a dataset exists for the provided key.

@param string $key
@return bool
Checks if a dataset exists for the provided key .