TypeError: only size -1 arrays can be converted to python scalar

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i am facing this error and am new to python. not sure how am not supposed to enter a matrix as the input ( image) this is the code :

   import cv2
   import matplotlib.pyplot as plt
   image = cv2.imread('sample.jpg')
   def show_rgb_hist(image):
             colours = ('r','g','b')
             for i, c in enumerate(colours):
             plt.figure(figsize=(20, 4))
             histr = cv2.calcHist([image], [i], None, [256], [0, 256])

             if c == 'r': colours = [((i/256, 0, 0)) for i in range(0, 256)]
             if c == 'g': colours = [((0, i/256, 0)) for i in range(0, 256)]
             if c == 'b': colours = [((0, 0, i/256)) for i in range(0, 256)]

             plt.bar(range(0, 256), histr, color=colours, edgecolor=colours, width=1)

             plt.show()

    x=show_rgb_hist(image)
   cv2.imshow('img', x)