<｜begin▁of▁sentence｜>### Instruction:
Given a graph which you can read from graph50.gml, can you use the 'VertexClustering.__len__' method to determine the number of clusters formed by the 'community_multilevel' clustering algorithm?
### Response:
from igraph import Graph

# Load a graph
g = Graph.Read_GML('graph50.gml')

# Create a clustering object
vc = g.community_multilevel()

# Get the number of clusters
num_clusters = len(vc)
print('Number of clusters:', num_clusters)
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