code: def do_internal_run(self):
          
          if not self.save_J:
              raise RuntimeError('self.save_J=True required for do_internal_run()')
          if not np.all(self._has_saved_J):
              raise RuntimeError('J, JTJ have not been pre-computed. Call do_run_1 or do_run_2')
          self._do_run(mode='internal')
docs: Calls LMParticles.do_internal_run for each group of particles.