chr2	test	exon	20	30	.	+	.	transcript_id "C"; gene_id "C";
chr1	test	exon	11	12	.	-	.	transcript_id "A_2"; gene_id "A_2";
chr1	test	exon	1	2	.	-	.	transcript_id "A_2"; gene_id "A_2";
chr2	test	CDS	26	28	.	+	.	transcript_id "C"; gene_id "C";