def METHOD_NAME(channel: ET.Element, previous: List[ET.Element], now: datetime):
    # Copy in previous items, if we have them.
    for item in previous:
        date_elem = item.find("./pubDate")
        if date_elem is None:
            # Item doesn't have a valid publication date?
            continue
        date = email.utils.parsedate_to_datetime(date_elem.text or "")
        if date + MAX_ITEM_AGE < now:
            # Item too old, get rid of it.
            continue
        channel.append(item)