code: def test_columnstack(teardown):
      x1 = Input()
      x2 = Input()
      y = ColumnStack()([x1, x2])
      model = Model([x1, x2], y)
  
      x1_data = np.array([1, 10, 100])
      x2_data = np.array([2, 20, 200])
  
      y_expected = np.column_stack([x1_data, x2_data])
  
      y_pred = model.predict([x1_data, x2_data])
  
      assert_array_equal(y_pred, y_expected)
  
file_path: baikal/tests/steps/test_merge.py
imports: import numpy
  import pytest
  from numpy.testing import assert_array_equal
  from baikal import Model, Input
  from baikal._core.utils import listify, safezip2
  from baikal.steps import ColumnStack, Concatenate, Stack, Split
  from tests.helpers.fixtures import teardown
label_desc: Use image node_id 1 for calling a global function with example usage: test_columnstack(teardown) without return types