code: def _x_reduced(self, x, y, n_sersic, r_eff, center_x, center_y):
          
          x_ = x - center_x
          y_ = y - center_y
          r = np.sqrt(x_**2 + y_**2)
          if isinstance(r, int) or isinstance(r, float):
              r = max(self._s, r)
          else:
              r[r < self._s] = self._s
          x_reduced = (r/r_eff)**(1./n_sersic)
          return x_reduced
docs: coordinate transform to normalized radius
          :param x:
          :param y:
          :param center_x:
          :param center_y:
          :return: