<｜begin▁of▁sentence｜>### Instruction:
As a mobile app tester, you have been tasked with evaluating and testing a mobile GPS navigation application across different devices and network conditions. The application utilizes a directed graph data structure to represent road networks, with edges defined by a list of tuples representing road connections. Your task is to utilize the NetworkX Python library to identify and list the successors of a specific vertex within this directed graph to ensure accurate navigation functionality.
### Response:
import networkx as nx

# Create a directed graph
dg = nx.DiGraph()
dg.add_edges_from([(1, 2), (1, 3), (3, 4)])

# Get the successors of vertex 1
successors_of_1 = list(dg.successors(1))

print('Successors of vertex 1:', successors_of_1)
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