<｜begin▁of▁sentence｜>### Instruction:
Given a simple graph with vertices connected linearly (0-1-2-3), can you use the AttributeSpecification class in igraph to create a vertex attribute called 'label' with alt_name 'vertex_label' where each label is defined as 'Node {index}', and the default label is 'undefined' in case of missing values?
### Response:
from igraph import Graph, AttributeSpecification

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

# Create an AttributeSpecification for a vertex attribute called 'label'
vertex_label_spec = AttributeSpecification(name='label',
                                            alt_name='vertex_label',
                                            default='undefined',
                                            transform=str)

# Apply the attribute specification to vertex 0 with a label attribute
def label_func(index):
    return f'Node {index}'

# Use the func parameter of AttributeSpecification to generate labels based on the vertex index
g.vs['label'] = [vertex_label_spec.func(i) for i in range(len(g.vs))]

# Print vertex labels
g.vs['label']
<|EOT|>
