code: def testRgbToGray(self):
      rgb_pixels = [[127, 127, 127], [255, 255, 255], [0, 0, 0]]
      result = rgb2gray(rgb_pixels)
  
      assert 3 == len(result)
      assert 127 == round(result[0])
      assert 255 == round(result[1])
      assert 0 == round(result[2])
  
imports: import unittest
  import matplotlib
  import numpy
  from pyclustering.cluster.kmeans import kmeans
  from pyclustering.cluster.center_initializer import kmeans_plusplus_initializer
  import pyclustering.utils
  from pyclustering.utils import euclidean_distance
  from pyclustering.utils import average_neighbor_distance
  from pyclustering.utils import read_sample
  from pyclustering.utils import data_corners
  from pyclustering.utils import norm_vector
  from pyclustering.utils import rgb2gray
  from pyclustering.utils import extract_number_oscillations
  from pyclustering.utils import draw_clusters
  from pyclustering.samples.definitions import SIMPLE_SAMPLES, IMAGE_SIMPLE_SAMPLES
label_desc: Use image node_id 12 for calling the Test obj's underlying member method code with example usage: obj.testRgbToGray() without return types