<｜begin▁of▁sentence｜>### Instruction:
Given a directed graph read from 'network.gml', how can you calculate the dyad census which classifies each pair of vertices into mutual, asymmetric, and null categories?
### Response:
from igraph import Graph

# Load a directed graph from 'network.gml'
g = Graph.Read_GML('network.gml')

# Calculate and print the dyad census of the graph
dyad_census = g.dyad_census()
print('Mutual:', dyad_census.mutual)
print('Asymmetric:', dyad_census.asymmetric)
print('Null:', dyad_census.null)
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