docs: def refine_cell(self, tilde_obj):
          '''
          NB only used for perovskite_tilting app
          '''
          try: lattice, positions, numbers = spg.refine_cell(tilde_obj['structures'][-1], symprec=self.accuracy, angle_tolerance=self.angle_tolerance)
          except Exception as ex:
              self.error = 'Symmetry finder error: %s' % ex
          else:
              self.refinedcell = Atoms(numbers=numbers, cell=lattice, scaled_positions=positions, pbc=tilde_obj['structures'][-1].get_pbc())
              self.refinedcell.periodicity = sum(self.refinedcell.get_pbc())
              self.refinedcell.dims = abs(det(tilde_obj['structures'][-1].cell))