code: static int elevation(IBond bond) {
          IBond.Stereo stereo = bond.getStereo();
          if (stereo == null) return 0;
          switch (stereo) {
              case UP:
              case DOWN_INVERTED:
                  return +1;
              case DOWN:
              case UP_INVERTED:
                  return -1;
              default:
                  return 0;
          }
      }
docs: Access the elevation of a bond.
  
  @param bond the bond
  @return +1 above the plane, 0 in the plane (default) or -1 below the
  plane