code: def prt_outfiles_grouped(self, outfiles):
          
          for outfile in outfiles:
              if outfile.endswith(".xlsx"):
                  self.wr_xlsx(outfile)
              elif outfile.endswith(".txt"):
                  self.wr_txt(outfile)
              else:
                  self.wr_tsv(outfile)
docs: Write to outfiles.