<｜begin▁of▁sentence｜>### Instruction:
As a technical illustrator creating technical drawings for a user manual, you need to set the bounding box for a graph plot within a canvas of 300x300 pixels. After that, you'll add a small random graph to the plot and save it in a file for the documentation.
### Response:
import igraph as ig
import cairo

# Initialize a Cairo surface and context
canvas_side_length = 300
surface = cairo.ImageSurface(cairo.FORMAT_ARGB32, canvas_side_length, canvas_side_length)
ctx = cairo.Context(surface)

# Create an igraph plot
plot = ig.Plot(surface)

# Set the bounding box for the plot
plot.bbox = (canvas_side_length, canvas_side_length)

# Create a small random graph
g = ig.Graph.GRG(20, 0.2)
# Add the graph to the plot
plot.add(g)

# Save the plot to a file
plot.save('random_graph.png')
<|EOT|>
