is $rdf.bnode() deprecated? Since it doesn't work for me. I can only use: `let x = new $rdf.BlankNode();` <img width="366" alt="bildschirmfoto 2019-02-25 um 09 35 40" src="https://user-images.githubusercontent.com/35169452/53324754-ea3a5800-38e1-11e9-8cf6-e05c40ac17e2.png">