def get_tag_values_from_ifds(tag_num, ifds):
    """
    Return values of a tag, if found in ifds. Return None otherwise.
    Assuming any tag exists only once in all ifds.
    """
    for key, ifd in ifds.items():
        if tag_num in ifd.tags:
            return ifd.tags[tag_num].values
    return None