code: def mask_6x6():
      """
      Generates a mask 6x6. It is all ones, besides the edges
  
      Returns
      -------
      out : ndarray
          3x5 uint8 image
      """
      img = np.ones((6, 6))
  
      img[:, 0] = 0
      img[:, -1] = 0
      img[0, :] = 0
      img[-1, :] = 0
      return img.astype(np.uint8)
  
file_path: solt/tests/fixtures.py
imports: import pytest
  import numpy
  from .utils import gen_gs_img_black_edge
label_desc: Use image node_id 13 for calling a global function with example usage: mask_6x6() and returns: img