import networkx as nx

def engranatge_exemple():
    g = nx.Graph()
    g.add_edges_from([('A', 'C'), ('E', 'F'), ('J', 'K'),
                      ('D', 'I'), ('I', 'H'), ('H', 'G')], unio='DENT')
    g.add_edges_from([('B', 'C'), ('C', 'D'), ('F', 'I')], unio='POL') 
    return g