<｜begin▁of▁sentence｜>### Instruction:
Given the `AbstractCairoVertexDrawer`, can you create a subclass that defines a custom drawing method for vertices in a graph? Assume the graph 'g' has been defined and you want to save the output in 'output.png'. Use the Kamada-Kawai layout ('kk') for setting up the positions of the vertices, and draw each vertex as a red filled circle with a black outline.
### Response:
import igraph as ig
from igraph.drawing import Plot
import cairo

# Assuming 'g' is the graph object we want to draw

# Set up plotting backend with cairo
backend = Plot('output.png', bbox=(600, 600), background='white')
context = backend.context

# Define the layout of the graph
layout = g.layout('kk')  # Kamada-Kawai layout

# Derive the bounding box for the drawing space
bbox = backend.bbox
palette = ig.drawing.colors.ClusterColoringPalette(len(g.vs['color']))

# Create a vertex drawer object that inherits from AbstractCairoVertexDrawer
class CustomVertexDrawer(ig.drawing.vertex.AbstractCairoVertexDrawer):
    def __init__(self, context, bbox, palette, layout):
        super().__init__(context, bbox, palette, layout)

    def draw(self, vertex, vertex_shape=None):
        # Here we define how to draw the vertex
        # for example, draw a circle for each vertex
        x, y = self.layout[vertex]
        context.arc(x, y, 10, 0, 2 * 3.1416)
        context.set_source_rgb(1, 0, 0)
        context.fill_preserve()
        context.set_source_rgb(0, 0, 0)
        context.stroke()

# Instantiate the custom drawer
vertex_drawer = CustomVertexDrawer(context, bbox, palette, layout)

# Now let's draw a specific vertex
vertex_drawer.draw(vertex=0)

# Finish by flushing the context
context.flush()

# Save the plotackend.save()
<|EOT|>
