code: def test_base_classifier_fit():
      """Test function for the BaseClassifier class fit.
  
      Test fit. It should:
      1. Work with 2D, 3D and DataFrame for X and nparray for y.
      2. Calculate the number of classes and record the fit time.
      3. have self.n_jobs set or throw  an exception if the classifier can
      multithread.
      4. Set the class dictionary correctly.
      5. Set is_fitted after a call to _fit.
      6. Return self.
      """
      dummy = _DummyClassifier()
      cases = 5
      length = 10
      test_X1 = np.random.uniform(-1, 1, size=(cases, length))
      test_X2 = np.random.uniform(-1, 1, size=(cases, 2, length))
      test_X3 = _create_example_dataframe(
          cases=cases, dimensions=1, length=length
      )
      test_X4 = _create_example_dataframe(
          cases=cases, dimensions=3, length=length
      )
      test_y1 = np.random.randint(0, 2, size=(cases))
      test_y2 = pd.DataFrame({"0": [1] * cases, "1": [0] * cases})
      result = dummy.fit(test_X1, test_y1)
      assert result is dummy
      result = dummy.fit(test_X3, test_y2)
      assert result is dummy
      with pytest.raises(ValueError, match=multivariate_message):
          result = dummy.fit(test_X2, test_y1)
      assert result is dummy
      result = dummy.fit(test_X3, test_y1)
      assert result is dummy
      with pytest.raises(ValueError, match=multivariate_message):
          result = dummy.fit(test_X4, test_y1)
      assert result is dummy
  
imports: import pickle
  import numpy
  import pandas
  import pytest
  from sklearn.model_selection import KFold
  from sktime.classification.base import BaseClassifier
  from sktime.classification.deep_learning.base import BaseDeepClassifier
  from sktime.classification.distance_based import KNeighborsTimeSeriesClassifier
  from sktime.classification.dummy import DummyClassifier
  from sktime.utils._testing.estimator_checks import _assert_array_almost_equal
  from sktime.utils._testing.panel import _make_classification_y, _make_panel, make_classification_problem
  from sktime.utils.validation._dependencies import _check_soft_dependencies
label_desc: Use image node_id 1 for calling a global function with example usage: test_base_classifier_fit() without return types