code: def _transcript_feature_positions(self, feature):
          
          ranges = self._transcript_feature_position_ranges(
              feature, required=True)
          results = []
          # a feature (such as a stop codon), maybe be split over multiple
          # contiguous ranges. Collect all the nucleotide positions into a
          # single list.
          for (start, end) in ranges:
              # since ranges are [inclusive, inclusive] and
              # Python ranges are [inclusive, exclusive) we have to increment
              # the end position
              for position in range(start, end + 1):
                  assert position not in results, \
                      "Repeated position %d for %s" % (position, feature)
                  results.append(position)
          return results
docs: Get unique positions for feature, raise an error if feature is absent.