old_contents: # RGB -> Gray
  
  import cv2
  import os
  from plantcv.plantcv import params
  from plantcv.plantcv._debug import _debug
  
  
  def rgb2gray(rgb_img):
      """Convert image from RGB colorspace to Gray.
  
      Inputs:
      rgb_img    = RGB image data
  
      Returns:
      gray   = grayscale image
  
      :param rgb_img: numpy.ndarray
      :return gray: numpy.ndarray
      """
  
      gray = cv2.cvtColor(rgb_img, cv2.COLOR_BGR2GRAY)
  
      _debug(visual=gray, filename=os.path.join(params.debug_outdir, str(params.device) + "_gray.png"))
  
      return gray
new_contents: # RGB -> Gray
  
  import cv2
  import os
  from plantcv.plantcv import params
  from plantcv.plantcv._debug import _debug
  
  
  def rgb2gray(rgb_img):
      """Convert image from RGB colorspace to Gray.
  
      Inputs:
      rgb_img    = RGB image data
  
      Returns:
      gray   = grayscale image
  
      :param rgb_img: numpy.ndarray
      :return gray: numpy.ndarray
      """
  
      gray = cv2.cvtColor(rgb_img, cv2.COLOR_BGR2GRAY)
  
      _debug(visual=gray, filename=os.path.join(params.debug_outdir, str(params.device) + "_gray.png"))
  
      return gray
  
subject: Update plantcv/plantcv/rgb2gray.py