Multi-contig gff parsing: Range issue

[acarafat]

I am working with a GFF file that contains multiple contigs, but the ##sequence-region only shows for the contig 1 in the gff header info.

Currently, while using .get_seqid2size() from gff parser, present code relies on ##sequence-region tag, therefore it gets the range for rest of the contigs wrong.

It could be solved by not relying on the ##sequence-region, since many gff file generated by different programs may not contain this comment.

Also, do you take pull request?

Thank you for the excellent package.