code: def check_solver(self, image_x, image_y, kwargs_lens):
          
          source_x, source_y = self._lensModel.ray_shooting(image_x, image_y, kwargs_lens)
          dist = np.sqrt((source_x - source_x[0]) ** 2 + (source_y - source_y[0]) ** 2)
          return dist
docs: returns the precision of the solver to match the image position
  
          :param kwargs_lens: full lens model (including solved parameters)
          :param image_x: point source in image
          :param image_y: point source in image
          :return: precision of Euclidean distances between the different rays arriving at the image positions