simple_cycles needs a DiGraph. Keep it tiny.

Goal

Print the cycles in a three-city directed loop.

import networkx as nx
G = nx.DiGraph([('Nairobi', 'Mombasa'), ('Mombasa', 'Kisumu'), ('Kisumu', 'Nairobi')])
print(list(nx.simple_cycles(G)))

import networkx as nx
G = nx.DiGraph([('a', 'b'), ('b', 'c')])
print(list(nx.simple_cycles(G)))

import networkx as nx
print(nx.find_cycle(nx.cycle_graph(4)))

import networkx as nx
print(nx.cycle_basis(nx.cycle_graph(['Nairobi', 'Nakuru', 'Kisumu'])))