<｜begin▁of▁sentence｜>### Instruction:
Given a simple tree graph with 10 vertices where each node (except leaves) has 2 children, how can you draw the graph vertices using the Plotly backend in igraph with the PlotlyVerticesDrawer, where each vertex is drawn as a dot of size 20?
### Response:
from igraph import Graph
from igraph.drawing import PlotlyPlot
from igraph.drawing.vertex import PlotlyVerticesDrawer

# Create a simple graph
g = Graph.Tree(10, 2)

# Get the layout of the graph
layout = g.layout('rt')

# Create a plotly plot
plot = PlotlyPlot(g, bbox=(400, 400), layout=layout)

# Initialize the vertex drawer with the plot, no palette needed in this example
vertex_drawer = PlotlyVerticesDrawer(plot)

# Iterate over all vertices in the graph and draw them using the vertex drawer
dot_size = 20 # Example size for the dot representation
for v in range(g.vcount()):
    point = layout[v]
    vertex_drawer.draw(vertex=g.vs[v], coords=(point[0], point[1]), visual_vertex={'size': dot_size})
    # As draw_label is undocumented, we assume it would work similarly to draw,
    # possibly by providing the label text and position
    # vertex_drawer.draw_label(label=g.vs[v]['label'], coords=(point[0], point[1]))

# Show the graph plot
plot.show()
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