<｜begin▁of▁sentence｜>### Instruction:
Given a custom vertex drawer class that extends the AbstractCairoVertexDrawer class in igraph, how can you implement its draw method and use it to draw a simple graph on a Cairo context with a specified layout and save the result to an image file?
### Response:
import igraph as ig
from igraph.drawing import Plot
from igraph.drawing.vertex import AbstractCairoVertexDrawer

# Create a simple graph
g = ig.Graph.Tree(5, 2)

# Define the layout
layout = g.layout('kk')

# Initialize a Plot object with a given bounding box
plot = Plot(bbox=(300, 300))

# Get the Cairo context from the Plot object
context = plot.context

# Instantiate a custom vertex drawer deriving from AbstractCairoVertexDrawer
class CustomVertexDrawer(AbstractCairoVertexDrawer):
    def draw(self, vertex, vertex_index):
        # Custom drawing code comes here
        pass

# Create an instance of the custom drawer
custom_drawer = CustomVertexDrawer(context, bbox=plot.bbox, palette=plot.palette, layout=layout)

# Draw the graph using our custom vertex drawer
for vertex in range(g.vcount()):
    custom_drawer.draw(vertex, vertex)

# Save the plot
plot.save('custom_vertex_drawer.png')
<|EOT|>
