code: def update(self):
          
  
          s = self.extract()
          self.mean = s[2][0]
  
          self.gradient = None
          self.gradient_error = None
          self.gradient_relative_error = None
docs: Update this `~photutils.isophote.EllipseSample` instance with
          the intensity integrated at the (x0, y0) center position using
          bilinear integration. The local gradient is set to `None`.