def count_uppercase(s: str) -> int:
    """Return the number of uppercase letters in s.



    """


def all_fluffy(s: str) -> bool:
    """Return True iff every character in s is fluffy. Fluffy characters are those
    that appear in the word 'fluffy'.



    """


def add_underscores(s: str) -> str:
    """Return a string that contains the characters from s with an underscore added
    after every character except the last.



    """