code: def get_available_positions(self):
          
          available_positions = ["new"]
          layout = self.context.getLayout()
          used_positions = [int(slot["position"]) for slot in layout]
          if used_positions:
              used = [
                  pos for pos in range(1, max(used_positions) + 1) if
                  pos not in used_positions]
              available_positions.extend(used)
          return available_positions
docs: Return a list of empty slot numbers