How do I access the string inside my function python?

Trying to gain access to this string to test it if it has 3 or more blues "b" inside of it. ---Both test and three_or_more_blues are functions.----- I'm completely lost, any one got an idea? Please change my title if it doesn't fit my question. Not sure really how to ask the question. Thanks!

test(three_or_more_blues, "brrrrrbrrrrrb")