<｜begin▁of▁sentence｜>### Instruction:
{'Description': 'Given a graph whose edge set is [(1, 2), (1, 3), (2, 3)], find all the pairs of nodes that are not connected by an edge.', 'Solution': "The code example demonstrates how to use NetworkX to identify all non-existent edges in the graph. It creates a simple graph and then uses the 'non_edges' function to get an iterator of edges that are not present in the graph. This can be used to analyze the possible connections that have not been realized in a network or to identify potential edges to add in network expansion."}
### Response:
import networkx as nx

# Create a graph
G = nx.Graph()
G.add_edges_from([(1, 2), (1, 3), (2, 3)])

# List all non-existent edges (pairs of nodes that are not connected)
nonexistent_edges = list(nx.non_edges(G))
print('Non-existent edges in the graph:', nonexistent_edges)
<|EOT|>
