code: def test_bgr2gray():
      cv_bgr = cv.imread(tens_path)
      cv_bgr = caer.to_tensor(cv_bgr, cspace="bgr")
      gray = caer.bgr2gray(cv_bgr)
  
      assert len(gray.shape) == 2
      assert isinstance(gray, caer.Tensor)
      assert gray.is_gray()
  
file_path: caer/tests/color/test_bgr.py
imports: import caer
  import cv2
  import os
label_desc: Use image node_id 2 for calling a global function with example usage: test_bgr2gray() without return types