-- dump date	2015-02-09.160429
-- class	EnsEMBL::intron
-- table	intron
-- table	main
-- field 1	id
-- field 2	type
-- field 3	name
-- field 4	contig
-- field 5	start_pos
-- field 6	end_pos
-- field 7	strand
-- field 8	transcript_id
-- field 9	gene_id
-- header
-- id	type	name	contig	start_pos	end_pos	strand	transcript_id	gene_id