<｜begin▁of▁sentence｜>### Instruction:
If you have a famous graph instance, like 'Zachary's karate club', and you want to explore an undocumented method `convergence_field_size` which is a part of the GraphBase class in igraph, how would you use this method and display the result?
### Response:
from igraph import Graph

# Assuming we have an igraph Graph instance
graph = Graph.Famous('Zachary')

# Use the undocumented convergence_field_size method
field_size = graph.convergence_field_size()

# Print the result
print('Convergence field size:', field_size)
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