def extCheck( extention: str ) -> str:
    """
    Ensures a file extention includes the leading '.'
    This is just used to error trap the lazy programmer who wrote it.

    :param extention: file extention
    :type extention: str
    :return: Properly formatted file extention
    :rtype: str
    """
    if extention[ 0 ] != '.':
        extention = '.' + extention
    return extention