code: def make_C_from_F(F):
      C = defaultdict(list)
      for node, color in F.items():
          C[color].append(node)
  
      return C
  
file_path: networkx/networkx/algorithms/coloring/equitable_coloring.py
imports: from collections import defaultdict
  import networkx
label_desc: Use image node_id 3 for calling a global function with example usage: make_C_from_F(F) and returns: C