`export_gtf` returns only exons

[sbresnahan]

As the title notes, a GTF returned by export_gtf is incomplete and should contain entries for transcripts.

[timbitz]

Hi-- This seems reasonable I guess. Though I must admit, I was always pretty amused by those, as they are redundant info in the GTF format, since exon entries also have both transcript_id and gene_id entries. In fact I actually don't think transcript entries are required in GTF2.2 format (http://mblab.wustl.edu/GTF22.html). Is some downstream program throwing an error that they are missing?

[sbresnahan]

Yes, downstream programs may require transcript entries - e.g., SQANTI3.