def load_from_rdf_file(self, rdf_file):
        """Initialize given an RDF input file representing the hierarchy."

        Parameters
        ----------
        rdf_file : str
            Path to an RDF file.
        """
        self.graph = rdflib.Graph()
        self.graph.parse(os.path.abspath(rdf_file), format='nt')
        self.initialize()