Character vector indicating whether the spliced boundary
is to the left (L) or right (R) of the splice site
frag_exonic
IRangesList of exonic regions, one entry
per fragment
frag_intron
IRangesList of introns, one entry per fragment
include
Character string indicating whether considered fragments
should be all that overlap the splice site (all), those
that are spliced at the site (spliced) or those that are
not spliced, i.e. extend into the adjacent intron (unspliced)
counts
Logical indicating whether counts or indices of
compatible fragments should be returned