<｜begin▁of▁sentence｜>### Instruction:
As a materials engineer working in the aerospace industry, you're tasked with enhancing the performance and durability of aircraft components through the application of advanced materials science. One of your ongoing projects involves analyzing the structural integrity of aircraft components using network theory.

Imagine you're studying the interconnectedness of various components within an aircraft system represented as a graph. Each node in the graph represents a specific component, and edges represent the connections between them. For instance, nodes 0, 1, and 2 might represent critical control systems, while nodes 3, 4, and 5 correspond to structural elements.

To analyze the graph effectively, you utilize the NetworkX library, a powerful tool for studying complex networks. After computing cohesive blocks within the graph to identify clusters of closely connected components, you need to determine the parent group index for a particular cluster.

In this scenario, you'll leverage NetworkX's CohesiveBlocks module, specifically the `parent` function, to retrieve the parent group index. This index provides crucial insight into the hierarchical structure of the cohesive blocks, aiding in your understanding of the overall network topology and its implications for aircraft performance and safety.
### Response:
from igraph import Graph, CohesiveBlocks

# Create a simple undirected graph
g = Graph(edges=[(0, 1), (0, 2), (1, 2), (3, 4), (4, 5), (3, 5)])

# Initialize CohesiveBlocks
cb = CohesiveBlocks(g)

# Compute the cohesive blocks
cb = cb.calculate()

# Get the parent of a specific block
block_index = 1
parent_index = cb.parent(block_index)

print('The parent index of block', block_index, 'is:', parent_index)
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