code: def add_references(self, other_names):
          
          if not other_names:
              # Skip on empty list
              return
          with open(self.outfile, 'rt') as fp:
              header, body = self.split_header(fp)
          with open(self.outfile, 'wt') as fp:
              fp.writelines(header)
              fp.writelines(
                  '-r {0}.{1}\n'.format(other_name, OPTIONS['out_ext'])
                  for other_name in sorted(other_names)
              )
              fp.writelines(body)
docs: Add references to other_names in outfile