def intify_and_make_intron(junction):
    """Convert start and stop strings to ints and shorten the interval

    Interval is shortened to match the introns of SJ.out.tab files from STAR

    Parameters
    ----------
    junction : tuple
        (chrom, start, stop, strand) tuple of strings, e.g.
        ('chr1', '100', '200', '-')

    Returns
    -------
    intron : tuple
        (chrom, start, stop, strand) tuple of string, int, int, string.
        Adds 1 to original start and subtracts 1 from original stop

    >>> intify_and_make_intron(('chr1', '100', '200', '-'))
    ('chr1', 101, 199, '-')
    """
    chrom, start, stop, strand = junction
    start = int(start) + 1
    stop = int(stop) - 1
    return chrom, start, stop, strand