<｜begin▁of▁sentence｜>### Instruction:
Given a graph instance 'g' representing a social network, the provided code uses the CohesiveBlocks.hierarchy function from the igraph library to calculate and print the hierarchical relationships between cohesive groups within the network. The returned 'block_tree' graph is a directed tree where each edge indicates that one group is a superset of the other, with edges pointing from the larger group to the smaller one. How would you identify the largest group that encompasses all the others in this hierarchical tree?
### Response:
import igraph as ig

# Assume 'g' is an igraph.Graph instance
blocks = ig.CohesiveBlocks(g)
block_tree = blocks.hierarchy()

# Print the hierarchical relationships
print(block_tree)
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