This functon extract the neighborhood DNA regions of a GRangesList object. The neighborhood DNA regions represent the promoter region (5'end) and complementary DNA region on the 3'end, which we call "Tail" here. The 5'end neighborhood DNA can often be useful as a kind of negative control region that is not associated with a clear biological function.
Make a Guitar Coordinates from TranscriptDb object, i.e., making Guitar coordinates for 8 different components, including, 5'UTR, CDS, 3'UTR, lncRNA, Pomoter and Tail of mRNA and lncRNA. Additional filters will discard transcripts that are too short or has too much ambigous on Genome to increase the sensitivity of the analysis.
providing 
.