<｜begin▁of▁sentence｜>### Instruction:
Given a simple square graph with edges connecting vertices 0-1, 1-2, 2-3, and 3-0, can you use igraph's Graph.write function to save this graph to a file in GraphML format?
### Response:
from igraph import Graph
import igraph as ig

g = ig.Graph(edges=[(0, 1), (1, 2), (2, 3), (3, 0)])
# Write the graph to a file in GraphML format
filename = 'output_graph.graphml'
g.write(filename, format='graphml')
<|EOT|>
