code: def solver_penalty(self, kwargs_lens, kwargs_ps, kwargs_cosmo, tolerance):
          
          dist = self._param.check_solver(kwargs_lens, kwargs_ps, kwargs_cosmo)
          if dist > tolerance:
              return dist * 10**10
          return 0
docs: test whether the image positions map back to the same source position
          :param kwargs_lens:
          :param kwargs_ps:
          :return: add penalty when solver does not find a solution