<｜begin▁of▁sentence｜>### Instruction:
Given an instance of MyAttributeCollector initialized with vertices of a directed graph, can you use the __len__ method to find out the number of attributes collected?
### Response:
from igraph import Graph

# Create an example graph with attributes
g = Graph([(0, 1), (1, 2), (2, 3)], directed=True)
g.vs['attribute'] = ['value1', 'value2', 'value3', 'value4']

class MyAttributeCollector(AttributeCollectorBase):
    pass

# Initialize an attribute collector for vertex attributes
ac = MyAttributeCollector(g.vs)

# Get the number of attributes collected
attribute_count = len(ac)

print(f'Total number of attributes collected: {attribute_count}')
<|EOT|>
