def reverse(s: str) -> str:
# the s[::-1] reverse-slice idiom over a str (mirrors xs[::-1] for lists).
return s[::-1]
def is_palindrome(s: str) -> bool:
# reverse-slice used inside a larger expression.
return s == s[::-1]
def reverse_upper(s: str) -> str:
# compose with another string method.
return s.upper()[::-1]