code: def addAlleleOfGene(self, allele_id, gene_id, rel_id=None):
          
          if rel_id is None:
              rel_id = self.globaltt["is_allele_of"]
          self.graph.addTriple(allele_id, rel_id, gene_id)
          return
docs: We make the assumption here that if the relationship is not provided,
          it is a
          GENO:is_allele_of.
  
          Here, the allele should be a variant_locus, not a sequence alteration.
          :param allele_id:
          :param gene_id:
          :param rel_id:
          :return: