def check_len(wt: str, off: str) -> int:
    """Verify the lengths of guide and off target match returning the length

    Args:
        wt: the guide type guide sequence
        off: the off target sequence

    Returns:
        (int): the length of the data

    """
    wtl = len(wt)
    offl = len(off)
    assert (wtl == offl), "The lengths wt and off differ: wt = {}, off = {}".format(str(wtl), str(offl))
    return wtl