def set_percentage(x: Iterable[X], y: Iterable[X]) -> float:
a, b = set(x), set(y)<EOL>if not a:<EOL><INDENT>return <NUM_LIT:0.0><EOL><DEDENT>return len(a & b) / len(a)<EOL>
What percentage of x is contained within y?

    :param set x: A set
    :param set y: Another set
    :return: The percentage of x contained within y