docs: def get_elementary_intervals(self, features):
          """Generates a sorted list of elementary intervals"""
          coords = []
          try:
              for interval in features:
                  if len(interval) != 3:
                      raise SyntaxError('Interval malformed %s. Allways specify start and end position for interval.' % str(interval))
                  coords.extend([interval[0],interval[1]])    
          except IndexError:
              raise SyntaxError('Interval malformed %s. Allways specify start and end position for interval.' % str(interval))
          coords = list(set(coords))
          coords.sort()
          return coords