code: def test_linear_gradient_wrong_mode(self):
      # Arrange
      wrong_mode = "RGB"
  
      # Act / Assert
      with pytest.raises(ValueError):
          Image.linear_gradient(wrong_mode)
  
imports: import io
  import os
  import shutil
  import sys
  import tempfile
  import pytest
  from PIL import Image, ImageDraw, ImagePalette, UnidentifiedImageError
  from .helper import assert_image_equal, assert_image_equal_tofile, assert_image_similar_tofile, assert_not_all_same, hopper, is_win32, mark_if_feature_version, skip_unless_feature
label_desc: Use image node_id 37 for calling the TestImage obj's underlying member method code with example usage: obj.test_linear_gradient_wrong_mode() without return types