def usgs_lead_url_helper(*, year, **_):
    """
    This helper function uses the "build_url" input from flowbyactivity.py,
    which is a base url for data imports that requires parts of the url text
    string to be replaced with info specific to the data year. This function
    does not parse the data, only modifies the urls from which data is
    obtained.
    :param build_url: string, base url
    :return: list, urls to call, concat, parse, format into Flow-By-Activity
        format
    """
    if int(year) < 2013:
        build_url = ('https://d9-wret.s3.us-west-2.amazonaws.com/assets/'
                     'palladium/production/atoms/files/myb1-2016-lead.xls')
    elif int(year) < 2014:
        build_url = ('https://d9-wret.s3.us-west-2.amazonaws.com/assets/'
                     'palladium/production/atoms/files/myb1-2017-lead.xls')
    else:
        build_url = ('https://d9-wret.s3.us-west-2.amazonaws.com/assets/'
                     'palladium/production/s3fs-public/media/files/myb1-2018-lead-advrel.xlsx')
    url = build_url
    return [url]