<｜begin▁of▁sentence｜>### Instruction:
Given a graph with nodes that have a 'color' attribute, can you generate a set of unique known colors present in the graph? For example, if the graph has nodes with attributes {'1': {'color': 'blue'}, '2': {'color': 'red'}, '3': {'color': 'green'}}, you need to extract the set of unique colors {'blue', 'red', 'green'}.
### Response:
import networkx as nx

# Create a Graph
G = nx.Graph()

# Add nodes with color attribute
G.add_node(1, color='blue')
G.add_node(2, color='red')
G.add_node(3, color='green')

# Get a dictionary of nodes with their corresponding colors
node_colors = nx.get_node_attributes(G, 'color')

# Get the set of unique colors known in the graph
known_colors = set(node_colors.values())

# Print the known colors
print(known_colors)
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