code: def test_transform(self):
      # training data
      d = {"col1": ["a", "a", "c"]}
      df = pd.DataFrame(data=d)
      # fit encoder
      le = LabelEncoder()
      le.fit(df["col1"])
      # test data
      d_test = {"col2": ["c", "c", "a"]}
      df_test = pd.DataFrame(data=d_test)
      # transform
      y = le.transform(df_test["col2"])
      self.assertEqual(y[0], 1)
      self.assertEqual(y[1], 1)
      self.assertEqual(y[2], 0)
  
file_path: mljar-supervised/tests/tests_preprocessing/test_label_encoder.py
imports: import unittest
  import tempfile
  import json
  import numpy
  import pandas
  from supervised.preprocessing.label_encoder import LabelEncoder
label_desc: Use image node_id 2 for calling the LabelEncoderTest obj's underlying member method code with example usage: obj.test_transform() without return types