<｜begin▁of▁sentence｜>### Instruction:
Given a graph, possibly the famous Petersen graph, how can you determine the independence number, which is the size of the largest independent vertex set in the graph?
### Response:
import igraph as ig

# Assuming `g` is an instance of igraph.Graph loaded with vertices and edges
g = ig.Graph.Famous('Petersen')

# Calculate the independence number
independence_num = g.independence_number()

# Print the independence number of the graph
print('The independence number of the graph is:', independence_num)
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