code: def test_ColumnSelector():
      X1_in = np.ones((4, 8))
      X1_out = ColumnSelector(cols=(1, 3)).transform(X1_in)
      assert X1_out.shape == (4, 2)
  
file_path: mlxtend/mlxtend/feature_selection/tests/test_column_selector.py
imports: import numpy
  import pandas
  from packaging.version import Version
  from sklearn import __version__
  from sklearn import datasets
  from sklearn.linear_model import LogisticRegression
  from sklearn.model_selection import GridSearchCV
  from sklearn.pipeline import make_pipeline
  from mlxtend.feature_selection import ColumnSelector
label_desc: Use image node_id 1 for calling a global function with example usage: test_ColumnSelector() without return types