code: def genes(self, contig=None, strand=None):
          
          gene_ids = self.gene_ids(contig=contig, strand=strand)
          return [self.gene_by_id(gene_id) for gene_id in gene_ids]
docs: Returns all Gene objects in the database. Can be restricted to a
          particular contig/chromosome and strand by the following arguments:
  
          Parameters
          ----------
          contig : str
              Only return genes on the given contig.
  
          strand : str
              Only return genes on this strand.