docs: def get_exon_ranges_for_transcript(self, transcript_id):
          """ obtain the sequence for a transcript from ensembl
          """
          
          headers = {"content-type": "application/json"}
          
          self.attempt = 0
          ext = "/overlap/id/{}?feature=exon".format(transcript_id)
          r = self.ensembl_request(ext, headers)
          
          exon_ranges = []
          for exon in json.loads(r):
              if exon["Parent"] != transcript_id:
                  continue
              
              start = exon["start"]
              end = exon["end"]
              
              exon_ranges.append((start, end))
          
          return exon_ranges