code: def extend_with(self, rdf_file):
          
          self.graph.parse(os.path.abspath(rdf_file), format='nt')
          self.initialize()
docs: Extend the RDF graph of this HierarchyManager with another RDF file.
  
          Parameters
          ----------
          rdf_file : str
              An RDF file which is parsed such that the current graph and the
              graph described by the file are merged.