code: def test_fail_array_fit():
      pca = KPCA(n_components=2)
      with pytest.raises(ValueError):
          pca.fit(X1[1])
  
file_path: mlxtend/mlxtend/feature_extraction/tests/test_kernel_pca.py
imports: import numpy
  import pytest
  from numpy.testing import assert_almost_equal
  from sklearn.datasets import make_moons
  from mlxtend.feature_extraction import RBFKernelPCA
label_desc: Use image node_id 7 for calling a global function with example usage: test_fail_array_fit() without return types