<｜begin▁of▁sentence｜>### Instruction:
As a jewelry appraiser, you might be asked to evaluate and appraise a unique piece of jewelry that contains a rare gemstone. Your client would like to have an image of the jewelry piece with a circle drawn directly over the gemstone to indicate the gemstone's size. Using your expertise with the igraph library, you may be tasked with creating an image file that includes this circle at a specified position with a given radius, providing a visual representation of the gemstone's dimensions.
### Response:
import igraph as ig
from igraph.drawing import Plot
from igraph.drawing.shapes import CircleDrawer

# Create a simple graph with 3 vertices and 3 edges
graph = ig.Graph(edges=[(0, 1), (1, 2), (2, 0)])

# Create a Plot object
plot = Plot()

# We need a CircleDrawer object to draw the circle
# Note that we don't use `CircleDrawer` directly to draw on plots; this is a low-level example.
circle_drawer = CircleDrawer(plot.context)

# Set the position and radius for our circle
circle_drawer.draw_path((50, 50), 30)

# To actually draw the path, we need to stroke or fill it.
# Here we choose to stroke the path with a line width of 2.
plot.context.set_line_width(2)
plot.context.stroke()

# Save the plot object to an image file
plot.save('circle.png')
<|EOT|>
