code: def get_gene2aart(gene2section2gos, sec2chr):
          
          geneid2str = {}
          for geneid, section2gos_gene in gene2section2gos.items():
              letters = [abc if s in section2gos_gene else "." for s, abc in sec2chr.items()]
              geneid2str[geneid] = "".join(letters)
          return geneid2str
docs: Return a string for each gene representing GO section membership.