ignore error annotation

            #The first intron is f_feature_num, and the last intron is l_feature_num-1, 

            #whatever the f_feature_type or l_feature_type is exon or intron.

            for intron_num in range(f_feature_num, l_feature_num):

                try:

                    intron_pos3, intron_id = intron_datas[intron_num-1]

                    retention = 1 if intron_num in retention_introns else 0

                    rel_pos = rel_gene_pos3 - intron_pos3

                    r = [intron_id, mRNA_intron_num, intron_num, rel_pos, retention, read_id]

                    o.write("\t".join([str(s) for s in r]) + "\n")

                except IndexError:

                    print(mRNA)

def read_by_column_names(filein, select_column_names, sep="\t"):