code: def test_empty_pool(create_X_y):
      pool_classifiers = []
      X, y = create_X_y
  
      with pytest.raises(ValueError):
          ds = BaseDS(pool_classifiers)
          ds.fit(X, y)
  
imports: import unittest.mock
  from unittest.mock import Mock, MagicMock
  import numpy
  import pytest
  from sklearn.exceptions import NotFittedError
  from sklearn.neighbors import KNeighborsClassifier
  from deslib.base import BaseDS
  from deslib.util.dfp import frienemy_pruning_preprocessed
  from .conftest import create_base_classifier
label_desc: Use image node_id 14 for calling a global function with example usage: test_empty_pool(create_X_y) without return types