code: def symm_reduce(self, coords_set, threshold=1e-6):
          
          surf_sg = SpacegroupAnalyzer(self.slab, 0.1)
          symm_ops = surf_sg.get_symmetry_operations()
          unique_coords = []
          # Convert to fractional
          coords_set = [self.slab.lattice.get_fractional_coords(coords)
                        for coords in coords_set]
          for coords in coords_set:
              incoord = False
              for op in symm_ops:
                  if in_coord_list_pbc(unique_coords, op.operate(coords),
                                       atol=threshold):
                      incoord = True
                      break
              if not incoord:
                  unique_coords += [coords]
          # convert back to cartesian
          return [self.slab.lattice.get_cartesian_coords(coords)
                  for coords in unique_coords]
docs: Reduces the set of adsorbate sites by finding removing
          symmetrically equivalent duplicates
  
          Args:
              coords_set: coordinate set in cartesian coordinates
              threshold: tolerance for distance equivalence, used
                  as input to in_coord_list_pbc for dupl. checking