<｜begin▁of▁sentence｜>### Instruction:
Given a simple graph with one vertex, how can you assign an attribute to this graph and retrieve its attributes using the Graph.attributes method?
### Response:
from igraph import Graph

# Create a simple graph with one vertex
simple_graph = Graph()
simple_graph.add_vertices(1)

# Assign an attribute to the graph
simple_graph['date_created'] = '2023-04-01'

# Retrieve and print all graph attributes
attributes = simple_graph.attributes()
print('Graph Attributes:', attributes)
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