code: def _cv_checkerboard(image_size, square_size, dtype=np.float64):
      """Generates a checkerboard level set function.
  
      According to Pascal Getreuer, such a level set function has fast
      convergence.
      """
      yv = np.arange(image_size[0], dtype=dtype).reshape(
          image_size[0], 1
      )
      xv = np.arange(image_size[1], dtype=dtype)
      sf = np.pi / square_size
      xv *= sf
      yv *= sf
      return np.sin(yv) * np.sin(xv)
  
file_path: scikit-image/skimage/segmentation/_chan_vese.py
imports: import numpy
  from scipy.ndimage import distance_transform_edt
  from .._shared.utils import _supported_float_type
label_desc: Use image node_id 9 for calling a global function with example usage: _cv_checkerboard(image_size, square_size, dtype) and returns: unknown