<｜begin▁of▁sentence｜>### Instruction:
Imagine we're examining a supply network optimization scenario, where we have a distribution model consisting of 5 facilities, and each facility is directly connected to every other one, signifying a complete and unweighted supply chain network. To evaluate the efficiency of this network in terms of commodity flow, we're interested in calculating a key metric known as the Wiener index, which essentially sums up all the shortest path distances between pairs of facilities. Using NetworkX, how might we go about determining the Wiener index for this particular distribution network?
### Response:
import networkx as nx

# Create an unweighted complete graph with 5 nodes
G = nx.complete_graph(5)

# Calculate the Wiener index of the graph
wiener_index = nx.wiener_index(G)

print('Wiener index of the graph:', wiener_index)
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