Utilities for reading and writing GTF format gene annotations
Read a GTF annotation file. The entire file is read at once,
because a single annotated transcript can span many lines in a GTF
file that are not required to occur in any specific order. The
SpliceSeqLoc transcript location is assembled from
exon annotations and any CDS location is then produced from
annotations, with an error occurring if the CDS is not a single
contiguous location within the transcript.