code: def write_uniques(path, prefix, uniques):
      
      for group in uniques:
          fp = osp.join(path, "{}_{}.txt".format(prefix, group))
          with open(fp, "w") as outf:
              outf.write("\n".join(uniques[group]))
docs: Given a path, the method writes out one file for each group name in the
      uniques dictionary with the file name in the pattern
  
          PATH/prefix_group.txt
  
      with each file containing the unique OTUIDs found when comparing that group
      to all the other groups in uniques.
  
      :type path: str
      :param path: Output files will be saved in this PATH.
  
      :type prefix: str
      :param prefix: Prefix name added in front of output filename.
  
      :type uniques: dict
      :param uniques: Output from unique_otus() function.