def METHOD_NAME(complaints):
    """Build a Slack block to alert maintainers to pay attention."""
    maintainers = set()
    for complaint in complaints:
        maintainers.update(complaint.maintainers)
    maintainers_block = {
        "type": "section",
        "text": {
                "type": "mrkdwn",
                "text": "Hi, this is Sir Complains-a-Lot. I need to speak to " +
                        (", ".join("<@{0}>".format(m)
                                   for m in maintainers)) + "."
        }
    }
    return maintainers_block