code: def __init__(self):
      self.total_attacks = 0
      self.all_num_words = None
      self.perturbed_word_percentages = None
      self.num_words_changed_until_success = 0
      self.all_metrics = {}
  
file_path: TextAttack/textattack/metrics/attack_metrics/words_perturbed.py
imports: import numpy
  from textattack.attack_results import FailedAttackResult, SkippedAttackResult
  from textattack.metrics import Metric
label_desc: Use image node_id 1 to create a new WordsPerturbed object from inherited base classes: Metric with example: obj = WordsPerturbed()