docs: def get_genomic_seq_for_transcript(self, transcript_id, expand):
          """ obtain the sequence for a transcript from ensembl
          """
          
          headers = {"content-type": "application/json"}
          
          self.attempt = 0
          ext = "/sequence/id/{0}?type=genomic;expand_3prime={1};expand_5prime={1}".format(transcript_id, expand)
          r = self.ensembl_request(ext, headers)
          
          gene = json.loads(r)
          
          seq = gene["seq"]
          seq_id = gene["id"]
          
          if seq_id != transcript_id:
              raise ValueError("ensembl gave the wrong transcript")
          
          desc = gene["desc"].split(":")
          chrom = desc[2]
          start = int(desc[3]) + expand
          end = int(desc[4]) - expand
          strand_temp = int(desc[5])
          
          strand = "+"
          if strand_temp == -1:
              strand = "-"
          
          return (chrom, start, end, strand, seq)