<｜begin▁of▁sentence｜>### Instruction:
Given an igraph Graph instance 'graph', how can you ensure that a specified layout (for instance 'fr' for Fruchterman-Reingold) is processed to be a valid igraph layout for drawing the graph using a matplotlib GraphDrawer?
### Response:
import igraph as ig

# Load example graph
graph = ig.Graph.Famous('Petersen')

# Initialize a GraphDrawer (here: plotting on Matplotlib)
drawer = ig.drawing.matplotlib.GraphDrawer()

# Ensure layout is an igraph Layout object or convert it
desired_layout = 'fr'
layout = drawer.ensure_layout(desired_layout, graph)

# Draw the graph with the layout
fig, ax = ig.plotting.matplotlib.utils.setup_axes()
drawer.draw(graph, layout, target=ax)
fig.show()
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