<｜begin▁of▁sentence｜>### Instruction:
Given a graph stored in 'network.gml', how can you use the 'cohesive_blocks' function in igraph to determine the graph's hierarchical subsets of vertices based on their structural cohesion and print them ordered by their level of cohesion?
### Response:
```python
from igraph import Graph

# Read the graph from a file
graph = Graph.Read('network.gml')

# Calculate the cohesive block structure of the graph
cblocks = graph.cohesive_blocks()

# Print the cohesive blocks ordered by their level of cohesion
for level, blocks_at_this_level in enumerate(cblocks):
    print('Level {}:'.format(level), blocks_at_this_level)
```
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