def clean_tokens(tokens):
  """Tokens are lower-cased, stripped of punctuation, and filtered for NULL."""
  tokens = [w.lower().strip(string.punctuation) for w in tokens]
  tokens = [w for w in tokens if w]
  tokens = tokens or ["NULL"]
  return tokens
Tokens are lower-cased, stripped of punctuation, and filtered for NULL.
language/capwap/utils/metric_utils.py