code: def dump_model(self, fout, fmap='', with_stats=False, dump_format="text"):
          
          if isinstance(fout, STRING_TYPES):
              fout = open(fout, 'w')
              need_close = True
          else:
              need_close = False
          ret = self.get_dump(fmap, with_stats, dump_format)
          if dump_format == 'json':
              fout.write('[\n')
              for i, _ in enumerate(ret):
                  fout.write(ret[i])
                  if i < len(ret) - 1:
                      fout.write(",\n")
              fout.write('\n]')
          else:
              for i, _ in enumerate(ret):
                  fout.write('booster[{}]:\n'.format(i))
                  fout.write(ret[i])
          if need_close:
              fout.close()
docs: Dump model into a text or JSON file.
  
          Parameters
          ----------
          fout : string
              Output file name.
          fmap : string, optional
              Name of the file containing feature map names.
          with_stats : bool, optional
              Controls whether the split statistics are output.
          dump_format : string, optional
              Format of model dump file. Can be 'text' or 'json'.