<｜begin▁of▁sentence｜>### Instruction:
Given a directed graph represented as a cycle of 5 nodes, and an edge with a negative weight added from node 1 to node 2, does this graph contain a negative edge cycle?
### Response:
import networkx as nx

G = nx.cycle_graph(5, create_using=nx.DiGraph())
G.add_edge(1, 2, weight=-7)
negative_cycle_exists = nx.negative_edge_cycle(G, weight='weight')
print('Does a negative edge cycle exist?', negative_cycle_exists)
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