class_docstr: Test class for custom learner tests.
class_docstr_tok: ["Test","class","for","custom","learner","tests","."]
docstr: Create necessary directories for testing.
docstr_tok: ["Create","necessary","directories","for","testing","."]
code: def setUpClass(cls):
      """Create necessary directories for testing."""
      for dir_path in [train_dir, test_dir, output_dir]:
          dir_path.mkdir(exist_ok=True)
  
file_path: skll/tests/test_custom_learner.py
imports: import csv
  import unittest
  from itertools import chain
  import numpy
  from numpy.testing import assert_array_equal
  from skll.data import NDJWriter
  from skll.experiments import run_configuration
  from skll.learner import Learner
  from skll.utils.testing import config_dir, fill_in_config_paths, make_classification_data, other_dir, output_dir, test_dir, train_dir, unlink
label_desc: Use image node_id 1 for calling the TestCustomLearner obj's underlying member method code with example usage: obj.setUpClass(cls) without return types