<｜begin▁of▁sentence｜>### Instruction:
Given a MultiDict object created with pairs [('key1', 'value1'), ('key2', 'value2'), ('key1', 'value3')], how would you calculate and print the number of distinct keys in this MultiDict using the __len__ method?
### Response:
from multidict import MultiDict

# Create a MultiDict object
d = MultiDict([('key1', 'value1'), ('key2', 'value2'), ('key1', 'value3')])

# Use __len__ to get the number of distinct keys
print(len(d))
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