code: def __init__(self, mapping_path: Optional[str]):
      if mapping_path:
          local_mapping_path = pathmgr.get_local_path(mapping_path)
          with open(local_mapping_path) as json_file:
              self.mapping = json.load(json_file)
      else:
          self.mapping = LETTER_CHAR_MAPPING
  
file_path: AugLy/augly/text/augmenters/letter_replacement.py
imports: import json
  from typing import List, Optional
  from augly.text.augmenters.utils import get_aug_idxes, LETTER_CHAR_MAPPING, rejoin_words_and_whitespace, split_words_on_whitespace, validate_augmenter_params
  from augly.utils import pathmgr
  from augly.utils.libsndfile import install_libsndfile
  from nlpaug.augmenter.char import CharAugmenter
  from nlpaug.util import Action, Method
label_desc: Use image node_id 1 to create a new CharReplacement object  with example: obj = CharReplacement(mapping_path)