def METHOD_NAME(
    self, ticket: Any, comment: str, author: str, old_values: Dict[str, Any]
) -> None:
    """Called when a ticket is modified.
    `old_values` is a dictionary containing the previous values of the
    fields that have changed.
    """
    if not (
        set(old_values.keys()).intersection(set(config.TRAC_NOTIFY_FIELDS))
        or (comment and "comment" in set(config.TRAC_NOTIFY_FIELDS))
    ):
        return
    content = f"{author} updated {markdown_ticket_url(ticket)}"
    if comment:
        content += f" with comment: {markdown_block(comment)}\n\n"
    else:
        content += ":\n\n"
    field_changes = []
    for key, value in old_values.items():
        if key == "description":
            content += "- Changed {} from {}\n\nto {}".format(
                key,
                markdown_block(value),
                markdown_block(ticket.values.get(key)),
            )
        elif old_values.get(key) == "":
            field_changes.append(f"{key}: => **{ticket.values.get(key)}**")
        elif ticket.values.get(key) == "":
            field_changes.append(f'{key}: **{old_values.get(key)}** => ""')
        else:
            field_changes.append(
                f"{key}: **{old_values.get(key)}** => **{ticket.values.get(key)}**"
            )
    content += ", ".join(field_changes)
    send_update(ticket, content)