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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:

def rle_encode(img:NPArrayMask)->str:
    "Return run-length encoding string from `img`."
    pixels = np.concatenate([[0], img.flatten() , [0]])
    runs = np.where(pixels[1:] != pixels[:-1])[0] + 1
    runs[1::2] -= runs[::2]
    return ' '.join(str(x) for x in runs)