code: def florentine_families_graph():
      """Returns Florentine families graph.
  
      References
      ----------
      .. [1] Ronald L. Breiger and Philippa E. Pattison
         Cumulated social roles: The duality of persons and their algebras,1
         Social Networks, Volume 8, Issue 3, September 1986, Pages 215-256
      """
      G = nx.Graph()
      G.add_edge("Acciaiuoli", "Medici")
      G.add_edge("Castellani", "Peruzzi")
      G.add_edge("Castellani", "Strozzi")
      G.add_edge("Castellani", "Barbadori")
      G.add_edge("Medici", "Barbadori")
      G.add_edge("Medici", "Ridolfi")
      G.add_edge("Medici", "Tornabuoni")
      G.add_edge("Medici", "Albizzi")
      G.add_edge("Medici", "Salviati")
      G.add_edge("Salviati", "Pazzi")
      G.add_edge("Peruzzi", "Strozzi")
      G.add_edge("Peruzzi", "Bischeri")
      G.add_edge("Strozzi", "Ridolfi")
      G.add_edge("Strozzi", "Bischeri")
      G.add_edge("Ridolfi", "Tornabuoni")
      G.add_edge("Tornabuoni", "Guadagni")
      G.add_edge("Albizzi", "Ginori")
      G.add_edge("Albizzi", "Guadagni")
      G.add_edge("Bischeri", "Guadagni")
      G.add_edge("Guadagni", "Lamberteschi")
      return G
  
imports: import networkx
label_desc: Use image node_id 3 for calling a global function with example usage: florentine_families_graph() and returns: G