How to use the plantcv.rgb2gray_hsv function in plantcv

def main():
  # Get options
  args = options()
  
  # Read image
  img, path, filename = pcv.readimage(args.image)
  #roi = cv2.imread(args.roi)
  
  # Pipeline step
  device = 0

  # Convert RGB to HSV and extract the Saturation channel
  device, s = pcv.rgb2gray_hsv(img, 's', device, args.debug)
  
  # Threshold the Saturation image
  device, s_thresh = pcv.binary_threshold(s, 36, 255, 'light', device, args.debug)
  
  # Median Filter
  device, s_mblur = pcv.median_blur(s_thresh, 0, device, args.debug)
  device, s_cnt = pcv.median_blur(s_thresh, 0, device, args.debug)
  
  # Fill small objects
  #device, s_fill = pcv.fill(s_mblur, s_cnt, 0, device, args.debug)
  
  # Convert RGB to LAB and extract the Blue channel
  device, b = pcv.rgb2gray_lab(img, 'b', device, args.debug)
  
  # Threshold the blue image
  device, b_thresh = pcv.binary_threshold(b, 137, 255, 'light', device, args.debug)

def main():
  # Get options
  args = options()
  
  # Read image
  img, path, filename = pcv.readimage(args.image)
  #roi = cv2.imread(args.roi)
  
  # Pipeline step
  device = 0

  # Convert RGB to HSV and extract the Saturation channel
  device, s = pcv.rgb2gray_hsv(img, 's', device, args.debug)
  
  # Threshold the Saturation image
  device, s_thresh = pcv.binary_threshold(s, 36, 255, 'light', device, args.debug)
  
  # Median Filter
  device, s_mblur = pcv.median_blur(s_thresh, 0, device, args.debug)
  device, s_cnt = pcv.median_blur(s_thresh, 0, device, args.debug)
  
  # Fill small objects
  #device, s_fill = pcv.fill(s_mblur, s_cnt, 0, device, args.debug)
  
  # Convert RGB to LAB and extract the Blue channel
  device, b = pcv.rgb2gray_lab(img, 'b', device, args.debug)
  
  # Threshold the blue image
  device, b_thresh = pcv.binary_threshold(b, 137, 255, 'light', device, args.debug)

def main():
  # Get options
  args = options()
  
  # Read image
  img, path, filename = pcv.readimage(args.image)
  #roi = cv2.imread(args.roi)
  
  # Pipeline step
  device = 0

  # Convert RGB to HSV and extract the Saturation channel
  device, s = pcv.rgb2gray_hsv(img, 's', device, args.debug)
  
  # Threshold the Saturation image
  device, s_thresh = pcv.binary_threshold(s, 36, 255, 'light', device, args.debug)
  
  # Median Filter
  device, s_mblur = pcv.median_blur(s_thresh, 0, device, args.debug)
  device, s_cnt = pcv.median_blur(s_thresh, 0, device, args.debug)
  
  # Fill small objects
  #device, s_fill = pcv.fill(s_mblur, s_cnt, 0, device, args.debug)
  
  # Convert RGB to LAB and extract the Blue channel
  device, b = pcv.rgb2gray_lab(img, 'b', device, args.debug)
  
  # Threshold the blue image
  device, b_thresh = pcv.binary_threshold(b, 137, 255, 'light', device, args.debug)

# Threshold the blue image
  device, b_thresh = pcv.binary_threshold(b, 138, 255, 'light', device, args.debug)
  device, b_cnt = pcv.binary_threshold(b, 138, 255, 'light', device, args.debug)
  
  # Fill small objects
  device, b_fill = pcv.fill(b_thresh, b_cnt, 150, device, args.debug)
  
  # Join the thresholded saturation and blue-yellow images
  device, bs = pcv.logical_and(s_fill, b_fill, device, args.debug)
  
  # Apply Mask (for vis images, mask_color=white)
  device, masked = pcv.apply_mask(img, bs,'white', device, args.debug)
    
  # Mask pesky brass piece
  device, brass_mask1 = pcv.rgb2gray_hsv(brass_mask, 'v', device, args.debug)
  device, brass_thresh = pcv.binary_threshold(brass_mask1, 0, 255, 'light', device, args.debug)
  device, brass_inv=pcv.invert(brass_thresh, device, args.debug)
  device, brass_masked = pcv.apply_mask(masked, brass_inv, 'white', device, args.debug)
  
  # Further mask soil and car
  device, masked_a = pcv.rgb2gray_lab(brass_masked, 'a', device, args.debug)
  device, soil_car1 = pcv.binary_threshold(masked_a, 128, 255, 'dark', device, args.debug)
  device, soil_car2 = pcv.binary_threshold(masked_a, 128, 255, 'light', device, args.debug)
  device, soil_car=pcv.logical_or(soil_car1, soil_car2,device, args.debug)
  device, soil_masked = pcv.apply_mask(brass_masked, soil_car, 'white', device, args.debug)
  
  # Convert RGB to LAB and extract the Green-Magenta and Blue-Yellow channels
  device, soil_a = pcv.rgb2gray_lab(soil_masked, 'a', device, args.debug)
  device, soil_b = pcv.rgb2gray_lab(soil_masked, 'b', device, args.debug)
  
  # Threshold the green-magenta and blue images

nir_img = An NIR grayscale image.
    debug   = None, print, or plot. Print = save to file, Plot = print to screen.

    :param vis_img: str
    :param nir_img: str
    :param debug: str
    :return:
    """
    # Read VIS image
    img, path, filename = pcv.readimage(vis_img)

    # Pipeline step
    device = 0

    # Convert RGB to HSV and extract the Saturation channel
    device, s = pcv.rgb2gray_hsv(img, 's', device, debug)

    # Threshold the Saturation image
    device, s_thresh = pcv.binary_threshold(s, 36, 255, 'light', device, debug)

    # Median Filter
    device, s_mblur = pcv.median_blur(s_thresh, 5, device, debug)
    device, s_cnt = pcv.median_blur(s_thresh, 5, device, debug)

    # Fill small objects
    # device, s_fill = pcv.fill(s_mblur, s_cnt, 0, device, args.debug)

    # Convert RGB to LAB and extract the Blue channel
    device, b = pcv.rgb2gray_lab(img, 'b', device, debug)

    # Threshold the blue image
    device, b_thresh = pcv.binary_threshold(b, 137, 255, 'light', device, debug)

def main():
  # Get options
  args = options()
  
  # Read image
  img, path, filename = pcv.readimage(args.image)
    
  # Pipeline step
  device = 0

  # Convert RGB to HSV and extract the Saturation channel
  device, s = pcv.rgb2gray_hsv(img, 's', device, args.debug)
  
  # Threshold the Saturation image
  device, s_thresh = pcv.binary_threshold(s, 36, 255, 'light', device, args.debug)
  
  # Median Filter
  device, s_mblur = pcv.median_blur(s_thresh, 0, device, args.debug)
  device, s_cnt = pcv.median_blur(s_thresh, 0, device, args.debug)
  
  # Fill small objects
  #device, s_fill = pcv.fill(s_mblur, s_cnt, 0, device, args.debug)
  
  # Convert RGB to LAB and extract the Blue channel
  device, b = pcv.rgb2gray_lab(img, 'b', device, args.debug)
  
  # Threshold the blue image
  device, b_thresh = pcv.binary_threshold(b, 137, 255, 'light', device, args.debug)

def main():
  # Get options
  args = options()
  
  # Read image
  img, path, filename = pcv.readimage(args.image)
    
  # Pipeline step
  device = 0

  # Convert RGB to HSV and extract the Saturation channel
  device, s = pcv.rgb2gray_hsv(img, 's', device, args.debug)
  
  # Threshold the Saturation image
  device, s_thresh = pcv.binary_threshold(s, 36, 255, 'light', device, args.debug)
  
  # Median Filter
  device, s_mblur = pcv.median_blur(s_thresh, 0, device, args.debug)
  device, s_cnt = pcv.median_blur(s_thresh, 0, device, args.debug)
  
  # Fill small objects
  #device, s_fill = pcv.fill(s_mblur, s_cnt, 0, device, args.debug)
  
  # Convert RGB to LAB and extract the Blue channel
  device, b = pcv.rgb2gray_lab(img, 'b', device, args.debug)
  
  # Threshold the blue image
  device, b_thresh = pcv.binary_threshold(b, 137, 255, 'light', device, args.debug)

def main():
  # Get options
  args = options()
  
  # Read image
  img, path, filename = pcv.readimage(args.image)
    
  # Pipeline step
  device = 0

  # Convert RGB to HSV and extract the Saturation channel
  device, s = pcv.rgb2gray_hsv(img, 's', device, args.debug)
  
  # Threshold the Saturation image
  device, s_thresh = pcv.binary_threshold(s, 36, 255, 'light', device, args.debug)
  
  # Median Filter
  device, s_mblur = pcv.median_blur(s_thresh, 0, device, args.debug)
  device, s_cnt = pcv.median_blur(s_thresh, 0, device, args.debug)
  
  # Fill small objects
  #device, s_fill = pcv.fill(s_mblur, s_cnt, 0, device, args.debug)
  
  # Convert RGB to LAB and extract the Blue channel
  device, b = pcv.rgb2gray_lab(img, 'b', device, args.debug)
  
  # Threshold the blue image
  device, b_thresh = pcv.binary_threshold(b, 137, 255, 'light', device, args.debug)

:param nir_img: str
    :param vis_traits: dict
    :param nir_traits: dict
    :param traits: dict
    :param debug: str
    :return: 
    """
    # Read image
    print ("starting processing...")
    img, path, filename = pcv.readimage(vis_img)
    brass_mask = cv2.imread('masks/mask_brass_tv_z1_L1.png')

    device = 0

    # Convert RGB to HSV and extract the Saturation channel
    device, s = pcv.rgb2gray_hsv(img, 's', device, debug)

    # Threshold the Saturation image
    device, s_thresh = pcv.binary_threshold(s, 75, 255, 'light', device, debug)

    # Median Filter
    device, s_mblur = pcv.median_blur(s_thresh, 5, device, debug)
    device, s_cnt = pcv.median_blur(s_thresh, 5, device, debug)

    # Fill small objects
    device, s_fill = pcv.fill(s_mblur, s_cnt, 150, device, debug)

    # Convert RGB to LAB and extract the Blue channel
    device, b = pcv.rgb2gray_lab(img, 'b', device, debug)

    # Threshold the blue image
    device, b_thresh = pcv.binary_threshold(b, 138, 255, 'light', device, debug)