code: def _get_ngram_counter(ids, n):
    
    # Remove zero IDs used to pad the sequence.
    ids = [token_id for token_id in ids if token_id != 0]
    ngram_list = [tuple(ids[i:i + n]) for i in range(len(ids) + 1 - n)]
    ngrams = set(ngram_list)
    counts = collections.Counter()
    for ngram in ngrams:
      counts[ngram] = 1
    return counts
docs: Get a Counter with the ngrams of the given ID list.
  
    Args:
      ids: np.array or a list corresponding to a single sentence
      n: n-gram size
  
    Returns:
      collections.Counter with ID tuples as keys and 1s as values.