class_docstr: Replaces words randomly with common misspellings, from a list of common misspellings.
  
  Perturbation example:
  
  **Input:**
      Already, the new product is not available.
  
  **Output:**
      Aready, the new product is not availible.
code: def perturb(self, text: str, rng: Random) -> str:
      def mispell(match: re.Match) -> str:
          word = match.group(1)
          if rng.random() < self.prob:
              mispelled_word = str(
                  rng.choice(self.correct_to_misspelling[word])
              )
              return match_case(word, mispelled_word)
          else:
              return word
  
      return self.mispelling_pattern.sub(mispell, text)
  
file_path: H2O/h2o_hf/helm/src/helm/benchmark/augmentations/misspelling_perturbation.py
imports: from dataclasses import dataclass
  import json
  from pathlib import Path
  import re
  from random import Random
  from typing import Dict, List
  from helm.common.general import match_case
  from .perturbation import Perturbation
  from .perturbation_description import PerturbationDescription
label_desc: Use image node_id 3 for calling the MisspellingPerturbation obj's underlying member method code with example usage: obj.perturb(text, rng) and returns: self, match_case, word