<｜begin▁of▁sentence｜>### Instruction:
Given a path graph with edge set [(0, 1), (1, 2), (2, 3)], how do you use NetworkX to write this graph into a GML file named 'path_graph.gml'?
### Response:
import networkx as nx

# Create a path graph with four nodes
G = nx.path_graph(4)

# Write the graph into a GML file
nx.write_gml(G, 'path_graph.gml')
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