code: def _check_stems(files):
      
      used = set()
      for fn in files:
          if os.path.basename(fn) in used:
              logger.warning("%s stem is multiple times in your file list, "
                           "so we don't know "
                           "how to assign it to the sample data in the CSV. "
                           "We are gonna use full path to make a difference, "
                           "that means paired files should be in the same folder. "
                           "If this is a problem, you should rename the files you want "
                           "to merge. Sorry, no possible magic here." % os.path.basename(fn)
                           )
              return True
          used.add(os.path.basename(fn))
      return False
docs: check if stem names are the same and use full path then