<｜begin▁of▁sentence｜>### Instruction:
Given an undirected graph generated with the "GRG" model (Geometric Random Graph) with 100 vertices and a radius of 0.2, can you draw the graph using the CairoGraphDrawer onto a 600x600 pixel image surface with a 20-pixel margin around the figure, and save it to 'graph.png'?
### Response:
```python
from igraph.drawing import Plot
from igraph.drawing.graph import CairoGraphDrawer
from igraph import Graph
import cairo

# Create an igraph graph
graph = Graph.GRG(100, 0.2)

# Set up Cairo context and bounding box
surface = cairo.ImageSurface(cairo.FORMAT_ARGB32, 600, 600)
context = cairo.Context(surface)
bbox = (20, 20, 580, 580)

# Create a CairoGraphDrawer
graph_drawer = CairoGraphDrawer(context, bbox)

# Draw the graph
graph_drawer.draw(graph)

# Save the image to a file
surface.write_to_png('graph.png')
```
<|EOT|>
