<｜begin▁of▁sentence｜>### Instruction:
As a helpful assistant with a good knowledge of the networkx library, you might need to visualize a simple directed graph with vertices 0 and 1, connected by an edge. To achieve this, you are interested in utilizing the functionality provided by the AlphaVaryingEdgeDrawer's draw_directed_edge method from the igraph library. This will enable you to visualize the edge with varying alpha (transparency) to enhance the clarity and visual appeal of the graph.

Your scenario involves presenting a network diagram that captures the connections between different components of a complex system, such as the communication pathways in a computer network or the flow of resources in a supply chain. Implementing varying alpha for the edges will allow you to represent the strength or frequency of interactions between the different components in the network, thereby offering valuable insights into the underlying patterns and dynamics.
### Response:
from igraph import Graph, plot
from igraph.drawing import AlphaVaryingEdgeDrawer

# Create a simple directed graph
g = Graph(directed=True)
g.add_vertices(2)
g.add_edges([(0, 1)])

# Prepare the plot
visual_style = {'vertex_size': 20, 'vertex_label': g.vs.indices}
pl = plot(g, **visual_style)

# Use the AlphaVaryingEdgeDrawer to draw a directed edge
alpha_edge_drawer = AlphaVaryingEdgeDrawer(pl.context)

# Get the visual properties for the edge and vertices
edge = g.es[0]
src_vertex = g.vs[edge.source]
dest_vertex = g.vs[edge.target]

# Call the draw_directed_edge method
alpha_edge_drawer.draw_directed_edge(edge, src_vertex, dest_vertex)

# Save the plot to a file
pl.save('directed_graph.png')
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