Create an easy data frame to allow easy annotation
    during differential expression analysis i.e
    gene:exon_id chr start end strand

def create_dexseq_annotation(gff, count_file):
    """
    Create an easy data frame to allow easy annotation
    during differential expression analysis i.e
    gene:exon_id chr start end strand
    """
    out_file = count_file + ".ann"
    if file_exists(out_file):
        return out_file
    with file_transaction(out_file) as tx_out:
        with open(tx_out, 'w') as out_handle:
            with open(gff) as in_handle:
                for line in in_handle:
                    cols = line.strip().split("\t")
                    if cols[2] == "exonic_part":
                        exon = [f for f in cols[8].split(";") if f.strip().startswith("exonic_part_number")]
                        gene = [f for f in cols[8].split(";") if f.strip().startswith("gene_id")]
                        exon = exon[0].replace("\"", "").split()[1]
                        gene = gene[0].replace("\"", "").split()[1]
                        length = int(cols[4]) - int(cols[3]) + 1
                        line = "%s:%s\t%s\t%s\t%s\t%s\t%s\t%s\n" % (gene, exon, gene,
                                                                    cols[0], cols[3],
                                                                    cols[4],
                                                                    length, cols[6])
                        out_handle.write(line)