code: def _set_box(self):
          
          net_volume = 0.0
          for idx, mol in enumerate(self.mols):
              length = max([np.max(mol.cart_coords[:, i])-np.min(mol.cart_coords[:, i])
                             for i in range(3)]) + 2.0
              net_volume += (length**3.0) * float(self.param_list[idx]['number'])
          length = net_volume**(1.0/3.0)
          for idx, mol in enumerate(self.mols):
              self.param_list[idx]['inside box'] = '0.0 0.0 0.0 {} {} {}'.format(
                  length, length, length)
docs: Set the box size for the molecular assembly