import re


def check_uuid(uuid):
    """Check if the string contains a proper UUID.

    Supported format: 71769af6-0a39-4242-94be-1f84f04c8a56
    """
    regex = re.compile(
        r'^[a-f0-9]{8}-?[a-f0-9]{4}-?4[a-f0-9]{3}-?[89ab][a-f0-9]{3}-?[a-f0-9]{12}\Z',
        re.I)
    match = regex.match(uuid)
    return bool(match)