code: def test_RGB(dtype):
      img = gaussian(data.text(), 1, preserve_range=False)
      imgR = np.zeros((img.shape[0], img.shape[1], 3), dtype=dtype)
      imgG = np.zeros((img.shape[0], img.shape[1], 3), dtype=dtype)
      imgRGB = np.zeros((img.shape[0], img.shape[1], 3), dtype=dtype)
      imgR[:, :, 0] = img
      imgG[:, :, 1] = img
      imgRGB[:, :, :] = img[:, :, None]
      r = np.linspace(136, 50, 100)
      c = np.linspace(5, 424, 100)
      init = np.array([r, c]).T
      snake = active_contour(
          imgR,
          init,
          boundary_condition="fixed",
          alpha=0.1,
          beta=1.0,
          w_line=-5,
          w_edge=0,
          gamma=0.1,
      )
      float_dtype = _supported_float_type(dtype)
      assert snake.dtype == float_dtype
      refr = [136, 135, 134, 133, 132, 131, 129, 128, 127, 125]
      refc = [5, 9, 13, 17, 21, 25, 30, 34, 38, 42]
      assert_equal(np.array(snake[:10, 0], dtype=np.int32), refr)
      assert_equal(np.array(snake[:10, 1], dtype=np.int32), refc)
      snake = active_contour(
          imgG,
          init,
          boundary_condition="fixed",
          alpha=0.1,
          beta=1.0,
          w_line=-5,
          w_edge=0,
          gamma=0.1,
      )
      assert snake.dtype == float_dtype
      assert_equal(np.array(snake[:10, 0], dtype=np.int32), refr)
      assert_equal(np.array(snake[:10, 1], dtype=np.int32), refc)
      snake = active_contour(
          imgRGB,
          init,
          boundary_condition="fixed",
          alpha=0.1,
          beta=1.0,
          w_line=-5 / 3.0,
          w_edge=0,
          gamma=0.1,
      )
      assert snake.dtype == float_dtype
      assert_equal(np.array(snake[:10, 0], dtype=np.int32), refr)
      assert_equal(np.array(snake[:10, 1], dtype=np.int32), refc)
  
file_path: scikit-image/skimage/segmentation/tests/test_active_contour_model.py
imports: import numpy
  import pytest
  from numpy.testing import assert_equal, assert_allclose
  from skimage import data
  from skimage._shared.utils import _supported_float_type
  from skimage.color import rgb2gray
  from skimage.filters import gaussian
  from skimage.segmentation import active_contour
label_desc: Use image node_id 4 for calling a global function with example usage: test_RGB(dtype) without return types