unique.feat(x, incomparables=FALSE, ...)feat, usually read from a genepred
file. Should have attributes labelled "transcript_id" which identify
features belonging to the same gene.feat with overlapping genes removed.
If the features are scored, then the feature with the highest score
is kept; otherwise the feature with the longest length. If
x is a pointer to an object stored in C, the return value will also
be a pointer (and x will be altered to the return value).