protected function getCache($documentId)
    {
        if (isset($this->cache[$documentId])) {
            return $this->cache[$documentId];
        }

        return null;
    }
protected function getCache($documentId)
    {
        if (isset($this->cache[$documentId])) {
            return $this->cache[$documentId];
        }

        return null;
    }
protected function getCache ( $ documentId ) { if ( isset ( $ this -> cache [ $ documentId ] ) ) { return $ this -> cache [ $ documentId ] ; } return null ; }
Get a document from this class' internal cache.

@param string $documentId ID to get from cache.
@return \Chill\Document[]|array|null
Get a document from this class internal cache .