code: def check_duplicate_filenames(files):
      
      # Check whether we'll have duplicates
      used_names = set()
      dup_names = list()
  
      for this_file in files:
          this_fname = os.path.basename(this_file)
          if this_fname in used_names:
              dup_names.append(this_file)
          else:
              used_names.add(this_fname)
  
      if len(dup_names) > 0:
          logger.warning(
              'Duplicate file name(s) found. Having duplicate file names will '
              'break some links. List of files: {}'.format(sorted(dup_names),))
docs: Check for duplicate filenames across gallery directories.