code: def get_gene(self, gene_name):
          
          if not gene_name:
              return
  
          gene_pk = self.genes.get(gene_name)
          if gene_pk:
              return gene_pk
  
          chrom = self.chromosomes[self.variants.chrom]
          gene = Gene.objects.find(gene_name, chrom, create=True)
          if gene:
              return gene.pk
docs: Get a gene from the cache or attempt to disambiguate or add a
          new record.