>>> import networkx as nx

# Creem el graf de l'exemple

>>> g = nx.Graph()
>>> g.add_nodes_from(['Besnak', 'Ashari', 'Samari', 'Krko',
...                   'Grenola', 'Filite', 'Miland', 'Loweh'])
>>> g.add_edges_from([ ('Besnak', 'Ashari'), ('Ashari','Samari'),
...                    ('Besnak', 'Krko'), ('Besnak', 'Grenola'),
...                    ('Grenola', 'Ashari'), ('Grenola', 'Samari'),
...                    ('Grenola', 'Krko'), ('Grenola', 'Miland'),
...                    ('Samari', 'Miland'), ('Miland', 'Loweh') ])

--inici--

>>> from mapes import zones_de_pas
>>> zones_de_pas(g, 'Besnak', 'Loweh')
{'Miland'}
>>> zones_de_pas(g, 'Krko', 'Filite')
{'IMPOSSIBLE'}
>>> zones_de_pas(g, 'Ashari', 'Miland')
set()

--fi--

>>> sorted(g.nodes())
['Ashari', 'Besnak', 'Filite', 'Grenola', 'Krko', 'Loweh', 'Miland', 'Samari']
>>> sorted( (sorted(e) for e in g.edges()) )
[['Ashari', 'Besnak'], ['Ashari', 'Grenola'], ['Ashari', 'Samari'], ['Besnak', 'Grenola'], ['Besnak', 'Krko'], ['Grenola', 'Krko'], ['Grenola', 'Miland'], ['Grenola', 'Samari'], ['Loweh', 'Miland'], ['Miland', 'Samari']]