Return histogram within binning of Histdd mh, with values looked up in this histogram.

        This is not rebinning: no interpolation /renormalization is performed.
        It's just a lookup.

def lookup_hist(self, mh):
        """Return histogram within binning of Histdd mh, with values looked up in this histogram.

        This is not rebinning: no interpolation /renormalization is performed.
        It's just a lookup.
        """
        result = mh.similar_blank_histogram()
        points = np.stack([mh.all_axis_bin_centers(i)
                           for i in range(mh.dimensions)]).reshape(mh.dimensions, -1)
        values = self.lookup(*points)
        result.histogram = values.reshape(result.histogram.shape)
        return result