code: def to_json(self):
      for k in self._vectorizer.vocabulary_.keys():
          self._vectorizer.vocabulary_[k] = int(
              self._vectorizer.vocabulary_[k]
          )
  
      data_json = {
          "new_columns": list(self._new_columns),
          "old_column": self._old_column,
          "vocabulary": self._vectorizer.vocabulary_,
          "fixed_vocabulary": self._vectorizer.fixed_vocabulary_,
          "idf": list(self._vectorizer.idf_),
      }
      return data_json
  
file_path: mljar-supervised/supervised/preprocessing/text_transformer.py
imports: import datetime
  import json
  import warnings
  import numpy
  import pandas
  from sklearn.feature_extraction.text import TfidfVectorizer
label_desc: Use image node_id 4 for calling the TextTransformer obj's underlying member method code with example usage: obj.to_json() and returns: data_json