<｜begin▁of▁sentence｜>### Instruction:
Imagine you're overseeing a facility with four key rooms laid out in a manner where room 1 is connected to room 2 and room 3, while room 2 and room 3 both have direct access to room 4. The connectivity between these rooms is critical to ensure smooth operations and security within the facility.

Now, you've been given a task to assess the security routes between two designated security zones within the facility. The first zone includes room 1 and 2, and the second zone encompasses room 3 and 4. Your objective is to evaluate the security coverage between these zones. 

Could you take a look at how many different pathways a security team would need to monitor in order to maintain a strong presence between these two critical zones? This would allow us to understand our security strength and ensure that we have adequate guard coverage along these potential transit points.
### Response:
import networkx as nx

# Create a graph
G = nx.Graph()

# Add nodes
G.add_nodes_from([1, 2, 3, 4])

# Add edges
G.add_edges_from([(1, 2), (1, 3), (2, 4), (3, 4)])

# Define two node sets
S = {1, 2}
T = {3, 4}

# Calculate edge expansion
expansion = nx.edge_expansion(G, S, T)

print('Edge expansion:', expansion)
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