code: def test_gray2luv():
      cv_gray = cv.imread(tens_path)
      cv_gray = cv.cvtColor(cv_gray, cv.COLOR_BGR2GRAY)
      luv = caer.gray2luv(cv_gray)
  
      assert len(luv.shape) == 3
      assert isinstance(luv, caer.Tensor)
      assert luv.is_luv()
  
file_path: caer/tests/color/test_gray.py
imports: import caer
  import cv2
  import os
label_desc: Use image node_id 7 for calling a global function with example usage: test_gray2luv() without return types