code: def tree_decomp(mol):
      n_atoms = mol.GetNumAtoms()
      if n_atoms == 1:  # special case
          return [[0]], []
  
      cliques = []
      for bond in mol.GetBonds():
          a1 = bond.GetBeginAtom().GetIdx()
          a2 = bond.GetEndAtom().GetIdx()
          if not bond.IsInRing():
              cliques.append([a1, a2])
  
      ssr = [list(x) for x in Chem.GetSymmSSSR(mol)]
      cliques.extend(ssr)
  
      nei_list = [[] for i in range(n_atoms)]
      for i in range(len(cliques)):
          for atom in cliques[i]:
              nei_list[atom].append(i)
  
      # Merge Rings with intersection > 2 atoms
      for i in range(len(cliques)):
          if len(cliques[i]) <= 2:
              continue
          for atom in cliques[i]:
              for j in nei_list[atom]:
                  if i >= j or len(cliques[j]) <= 2:
                      continue
                  inter = set(cliques[i]) & set(cliques[j])
                  if len(inter) > 2:
                      cliques[i].extend(cliques[j])
                      cliques[i] = list(set(cliques[i]))
                      cliques[j] = []
  
      cliques = [c for c in cliques if len(c) > 0]
      nei_list = [[] for i in range(n_atoms)]
      for i in range(len(cliques)):
          for atom in cliques[i]:
              nei_list[atom].append(i)
  
      # Build edges and add singleton cliques
      edges = defaultdict(int)
      for atom in range(n_atoms):
          if len(nei_list[atom]) <= 1:
              continue
          cnei = nei_list[atom]
          bonds = [c for c in cnei if len(cliques[c]) == 2]
          rings = [c for c in cnei if len(cliques[c]) > 4]
          # In general, if len(cnei) >= 3, a singleton should be added, but 1 bond + 2 ring is currently not dealt with.
          if len(bonds) > 2 or (len(bonds) == 2 and len(cnei) > 2):
              cliques.append([atom])
              c2 = len(cliques) - 1
              for c1 in cnei:
                  edges[(c1, c2)] = 1
          elif len(rings) > 2:  # Multiple (n>2) complex rings
              cliques.append([atom])
              c2 = len(cliques) - 1
              for c1 in cnei:
                  edges[(c1, c2)] = MST_MAX_WEIGHT - 1
          else:
              for i in range(len(cnei)):
                  for j in range(i + 1, len(cnei)):
                      c1, c2 = cnei[i], cnei[j]
                      inter = set(cliques[c1]) & set(cliques[c2])
                      if edges[(c1, c2)] < len(inter):
                          # cnei[i] < cnei[j] by construction
                          edges[(c1, c2)] = len(inter)
  
      edges = [u + (MST_MAX_WEIGHT - v,) for u, v in edges.items()]
      if len(edges) == 0:
          return cliques, edges
  
      # Compute Maximum Spanning Tree
      row, col, data = zip(*edges)
      n_clique = len(cliques)
      clique_graph = csr_matrix(
          (data, (row, col)), shape=(n_clique, n_clique)
      )
      junc_tree = minimum_spanning_tree(clique_graph)
      row, col = junc_tree.nonzero()
      edges = [(row[i], col[i]) for i in range(len(row))]
      return (cliques, edges)
  
imports: import rdkit
  import rdkit.Chem
  from scipy.sparse import csr_matrix
  from scipy.sparse.csgraph import minimum_spanning_tree
  from collections import defaultdict
  from rdkit.Chem.EnumerateStereoisomers import EnumerateStereoisomers, StereoEnumerationOptions
  from .vocab import Vocab
label_desc: Use image node_id 9 for calling a global function with example usage: tree_decomp(mol) and returns: cliques,  edges, list,  list, cliques,  edges