import re


def __get_driver_series_tag_text(tag):
    """
    Returns the driver series number from the given HTML tag

    Keyword Args:
    tag -- Device driver section header tag
    """
    driver_regex = re.compile('[0-9]+\.?[0-9]*\.?[0-9]*')
    match = driver_regex.search(tag.text)
    if match:
        match_text = tag.text[match.start():match.end()]
        if match_text[-1:] == ".":
            match_text = match_text[:-1]
        return match_text
    return None