multiple_top_level_parents.gff3

##gff-version 3
##sequence-region   ctg123 1 1497228
ctg123	.	mRNA	1050	9000	.	+	.	ID=mRNA1
ctg123	.	mRNA	1050	9000	.	+	.	ID=mRNA2
ctg123	.	exon	1050	1500	.	+	.	Parent=mRNA1,mRNA2
ctg123	.	mRNA	1300	9000	.	+	.	ID=mRNA3
ctg123	.	exon	1300	1500	.	+	.	Parent=mRNA3
ctg123	.	exon	3000	3902	.	+	.	Parent=mRNA1,mRNA3
ctg123	.	exon	5000	5500	.	+	.	Parent=mRNA1,mRNA2,mRNA3
ctg123	.	exon	7000	9000	.	+	.	Parent=mRNA1,mRNA2,mRNA3
###