def get_tail(raw_url_str):
    """
    Get final end chunk of https url- such as, for given "https:1/2/3/4.pdf,
    returns "4.pdf"
    :param raw_url_str: str
    :return: str
    """
    split = raw_url_str.split('/')
    if len(split[-1]) == 0:  # in case there's appended '/' at the end of url
        return split[-2]
    else:
        return split[-1]