<｜begin▁of▁sentence｜>### Instruction:
As an AutoCAD designer tasked with creating technical drawings, you're faced with a project that requires generating a visual representation of a tree structure. Specifically, you need to depict a tree graph with three levels and a branching factor of two. The challenge is to utilize the AbstractCairoDrawer feature in the iGraph API with Cairo to export this representation into a PNG file. Moreover, the final image should adhere to a custom bounding box size of 300x300 pixels.
### Response:
import cairo
from igraph import Graph, BoundingBox
from igraph.drawing import Plot

# Create a sample graph
g = Graph.Tree(3, 2)

# Define a bounding box
bbox = BoundingBox(300, 300)

# Setup Cairo surface and context
surface = cairo.ImageSurface(cairo.FORMAT_ARGB32, 300, 300)
context = cairo.Context(surface)

# Create a Plot object with the Cairo context and bounding box
plot = Plot(surface, bbox, background=None)

# Add our graph to the Plot
plot.add(g)

# Draw the plot to the Cairo context
plot.redraw()

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