code: def getLookupTable(self, img=None, n=None, alpha=None):
          
          if n is None:
              if img.dtype == np.uint8:
                  n = 256
              else:
                  n = 512
          if self.lut is None:
              self.lut = self.gradient.getLookupTable(n, alpha=alpha)
          return self.lut
docs: Return a lookup table from the color gradient defined by this
          HistogramLUTItem.