from typing import Optional


def prompt_yes_no(query: str, default: Optional[bool]) -> bool:
    """
    Asks the user a yes/no question and returns their choice.
    """

    if default is True:
        query += " [Y/n] "
    elif default is False:
        query += " [y/N] "
    else:
        query += " [y/n] "

    while True:
        response = input(query).strip().lower()
        if response == "y":
            return True
        elif response == "n":
            return False
        elif response == "" and default is not None:
            return default

        print("Please answer with 'y' or 'n'.")