<｜begin▁of▁sentence｜>### Instruction:
Given a graph read from 'graph_file.gml', how can you adjust the bounding box size for plotting the graph with a Cartesian coordinate system using the DescartesCoordinateSystem in igraph?
### Response:
from igraph import Graph, plot
from igraph.drawing import DescartesCoordinateSystem

# Load graph from file
graph = Graph.Read_GML('graph_file.gml')

# Create a plot with a Cartesian coordinate system
plot(graph, bbox=(0, 0, 300, 300), vertex_label=graph.vs['name'],
     margin=20, vertex_size=10,
     coordinate_system=DescartesCoordinateSystem())

# Set the bounding box of the Cartesian coordinate system
coord_system = DescartesCoordinateSystem(plot)
coord_system.bbox = (0, 0, 400, 400)
<|EOT|>
