code: def test_getchannel_wrong_params(self):
      im = hopper()
  
      with pytest.raises(ValueError):
          im.getchannel(-1)
      with pytest.raises(ValueError):
          im.getchannel(3)
      with pytest.raises(ValueError):
          im.getchannel("Z")
      with pytest.raises(ValueError):
          im.getchannel("1")
  
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 21 for calling the TestImage obj's underlying member method code with example usage: obj.test_getchannel_wrong_params() without return types