<｜begin▁of▁sentence｜>### Instruction:
Given a UniqueIdGenerator instance that has been used to generate a number of unique IDs, how can you determine the number of unique items that have been generated?
### Response:
from networkx.utils import UniqueIdGenerator

# Create a UniqueIdGenerator instance
uid_gen = UniqueIdGenerator()

# Use the UniqueIdGenerator to generate some unique IDs
for _ in range(5):
    print(uid_gen())

# Get the number of unique items generated
print('Number of unique items:', len(uid_gen))
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