code: def test_hsv2gray():
      cv_hsv = cv.cvtColor(cv_bgr, cv.COLOR_BGR2HSV)
      cv_hsv = caer.to_tensor(cv_hsv, cspace="hsv")
  
      gray = caer.hsv2gray(cv_hsv)
  
      assert len(gray.shape) == 2 or (
          len(gray.shape) == 3 and gray.shape[-1] == 1
      )
      assert isinstance(gray, caer.Tensor)
      assert gray.is_gray()
  
file_path: caer/tests/color/test_hsv.py
imports: import caer
  import cv2
  import os
label_desc: Use image node_id 3 for calling a global function with example usage: test_hsv2gray() without return types