def guess_sequence(redeem_script):
    '''
    str -> int
    If OP_CSV is used, guess an appropriate sequence
    Otherwise, disable RBF, but leave lock_time on.
    Fails if there's not a constant before OP_CSV
    '''
    try:
        script_array = redeem_script.split()
        loc = script_array.index('OP_CHECKSEQUENCEVERIFY')
        return int(script_array[loc - 1], 16)
    except ValueError:
        return 0xFFFFFFFE
str -> int
    If OP_CSV is used, guess an appropriate sequence
    Otherwise, disable RBF, but leave lock_time on.
    Fails if there's not a constant before OP_CSV