<｜begin▁of▁sentence｜>### Instruction:
As a plant breeder working on a farm, you have a network of irrigation systems connecting different fields. The edge set representing the connections between fields is [(Field A, Field B), (Field B, Field C), (Field C, Field D), (Field D, Field E), (Field E, Field A)]. Using the irrigation network, you need to determine the minimum number of irrigation valves that need to be turned on in order to ensure that all fields receive water. To do this, you can utilize the mincut and VertexCover APIs provided by the irrigation system management software.
### Response:
from igraph import Graph, VertexCover

# Create a simple graph
edges = [(0, 1), (1, 2), (2, 3), (3, 4), (4, 0)]
g = Graph(edges=edges)

# Find the minimum vertex cover using a heuristic method
vertex_cover = g.mincut().as_cover()
v_cover = VertexCover(g, vertex_cover)

# Get the size of the vertex cover
size = v_cover.size()
print('Size of the vertex cover:', size)
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