def get_added_after(
    fetch_full_feed, initial_interval, last_fetch_time=None, filter_args=None
):
    """
    Creates the added_after param, or extracts it from the filter_args
    :param fetch_full_feed: when set to true, will limit added_after
    :param initial_interval: initial_interval if no
    :param last_fetch_time: last_fetch time value (str)
    :param filter_args: set of filter_args defined by the user to be merged with added_after
    :return: added_after
    """
    if fetch_full_feed:
        return initial_interval

    if not filter_args or "added_after" not in filter_args:
        return last_fetch_time or initial_interval

    return filter_args["added_after"]