<｜begin▁of▁sentence｜>### Instruction:
As an industrial engineer focused on optimizing processes, systems, and operations for enhanced efficiency and productivity, imagine you're tasked with improving the layout visualization of a network diagram using the NetworkX library. Specifically, you're working with a graph employing a Kamada-Kawai layout, a popular method for arranging nodes. Now, you're seeking to manually incorporate a downward-facing triangle onto the plot without automatic filling or stroking. To achieve this, you need to utilize the DownTriangleDrawer function provided by NetworkX, maintaining control over the rendering of the triangle shape while adhering to the layout configuration.
### Response:
import igraph as ig
from igraph.drawing.shapes import DownTriangleDrawer

g = ig.Graph.Famous('C. elegans')
layout = g.layout('kk')  # Kamada-Kawai layout
visual_style = {'vertex_size': 7}

# Create plot object
plot = ig.Plot('down_triangle_graph.png', bbox=(300, 300), background='white')
plot.add(g, layout=layout, **visual_style)

# Create a DownTriangleDrawer object
context = plot.redraw(0)[0]
down_triangle = DownTriangleDrawer(context)

# Define a path to draw a down-facing triangle at a specific location
path = [(1, 1), (2, 3), (3, 1)]  # The vertices of the down triangle

down_triangle.draw_path(path)

# Commit the changes
context.stroke()

# Save and display the plot
plot.show()
<|EOT|>
