code: def test_custom_model(self):
      custom_model = {
          "a": "1",
          "b": "2",
      }
  
      custom_model_file_path = "char_keyboard_custom_model.json"
  
      with open(custom_model_file_path, "w") as outfile:
          json.dump(custom_model, outfile)
  
      text = "ababab"
      aug = nac.KeyboardAug(model_path=custom_model_file_path)
      augmented_data = aug.augment(text)
      augmented_text = augmented_data[0]
  
      self.assertTrue("1" in augmented_text or "2" in augmented_text)
  
      if os.path.exists(custom_model_file_path):
          os.remove(custom_model_file_path)
  
imports: import unittest
  import re
  import json
  import os
  import nlpaug.augmenter.char
label_desc: Use image node_id 15 for calling the TestKeyboard obj's underlying member method code with example usage: obj.test_custom_model() without return types