what does this function do? 

def add_grain(img, grain_size) -> Image.Image:
    pixels = np.asarray(img, dtype=np.float32) / 255.0
    inverted_pixels = ne.evaluate('1 - pixels')
    a_array = ne.evaluate('grain_size / (inverted_pixels + 1e-7)')
    b_array = ne.evaluate('grain_size / (pixels + 1e-7)')
    beta_distributed_array = DEF_RNG.beta(a_array, b_array)
    grainy_pixels = np.uint8(np.around(ne.evaluate('beta_distributed_array * 255')))
    return Image.fromarray(grainy_pixels) Add stress words which are capitalized. Limit those stress words for less than 18 times.
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