_:nc9fcd83cea7a4e529e0ad4e2a37a6f93xb2
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://git.skewed.de/count0/graph-tool/-/blob/e351c829b955257df56d36c992a8d1115525dd5c/src/graph/read_graphviz_new.cpp>