<｜begin▁of▁sentence｜>### Instruction:
Using a directed graph which can be read from 'graph.gml', assuming a heuristic function that returns zero (for simplicity), can you help calculate the shortest path from a source vertex with ID 0 to a target vertex with ID 5 using the A-Star algorithm?
### Response:
from igraph import Graph

# Create a graph instance (assuming Graph is from the igraph package)
g = Graph.Read_GML('graph.gml')

# Define a heuristic function
# For instance, a dummy heuristic function that always returns zero
heuristic = lambda graph, vertex1, vertex2: 0

# Calculate the shortest path from source to target using A* algorithm
# Replace 'source' and 'target' with the appropriate vertex IDs
path = g.get_shortest_paths_astar(source=0, target=5, heuristic_func=heuristic, weights=None)

# Print out the path
print('Shortest path (A*):', path)
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