wordcount.py exercise - how does word_count_tuple work in get_count()?

[Kyle Breneman]

I'm trying to understand all the parts of Google's solution here, but am having trouble wrapping my head around the purpose of "word_count_tuple", the argument in get_count().  How do any values get into word_count_tuple??  I don't see any place in the code where it is defined with values, or where values are added to it.