<｜begin▁of▁sentence｜>### Instruction:
As an industrial designer specializing in designing and developing products for mass production, you have been tasked with working on a project involving a network representation of a supply chain. The project involves using a file named 'network.lgl' to represent the network of suppliers, manufacturers, and distributors. Your goal is to read the contents of the 'network.lgl' file into an igraph object and identify all vertices that have a specific attribute name 'vertex_name'. This will help you in analyzing and optimizing the supply chain network for better efficiency and performance.
### Response:
import igraph as ig

# Read the LGL file to create a graph object
file_path = 'network.lgl'
g = ig.Graph.Read_Lgl(file_path, names=True, weights='if_present', directed=True)

# Extract a vertex set based on a specific attribute
desired_name = 'vertex_name'
vertices_with_desired_name = [v.index for v in g.vs if v['name'] == desired_name]

# Print the indices of vertices with the desired name
print(vertices_with_desired_name)
<|EOT|>
