def _add_gene_to_graph(self, gene, variant_bnode, gene_id, relation):
        """
        :param gene:
        :param variant_bnode:
        :return:
        """
        model = Model(self.graph)
        if gene_id:
            self.graph.addTriple(variant_bnode, relation, gene_id)
        elif gene:
            LOG.info("gene %s not mapped to NCBI gene, making blank node", gene)
            gene_bnode = self.make_id("{0}".format(gene), "_")
            model.addIndividualToGraph(gene_bnode, gene)
            self.graph.addTriple(variant_bnode, relation, gene_bnode)