code: def _add_gene_to_graph(self, gene, variant_bnode, gene_id, relation):
          
          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)
docs: :param gene:
          :param variant_bnode:
          :return: