code: def transform(self, x):
      return [self.remove_tone(s) for s in x]
  
imports: from sklearn.base import BaseEstimator, TransformerMixin
  import string
  import re
  from underthesea.pipeline.word_tokenize import tokenize
  from underthesea.utils.vietnamese_features import remove_tone
label_desc: Use image node_id 2 for calling the RemoveTone obj's underlying member method code with example usage: obj.transform(x) and returns: unknown