<｜begin▁of▁sentence｜>### Instruction:
Given a graph, how can you check if the graph has at least one vertex or not using the __bool__ method in igraph?
### Response:
from igraph import Graph
# Create a new undirected graph
g = Graph()
# Add 3 vertices to the graph
g.add_vertices(3)
# Check if the graph has at least one vertex
has_vertices = bool(g)
print('Graph has vertices:', has_vertices)
# Now create an empty graph
empty_g = Graph()
# Check if the empty graph has vertices
is_empty = not bool(empty_g)
print('Graph is empty:', is_empty)
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