def get_donor_acceptor(genome_d, chrom, strand, pos1, pos2):
    """
    pos1, pos2 would be the donor/acceptor, in 0-based index
    always pos1 < pos2
    if strand == '+': pos1 is the donor
    if strand == '-': pos1 is the acceptor

    :return: donor sequence (ex: "GT"), acceptor sequence (ex: "AG")
    """
    seq1 = genome_d[chrom][pos1+1:pos1+3].seq
    seq2 = genome_d[chrom][pos2-2:pos2].seq
    if strand == '+':
        return str(seq1).upper(), str(seq2).upper()
    else:
        return str(seq2.reverse_complement()).upper(), str(seq1.reverse_complement()).upper()