code: static StereoEncoder axialEncoder(IAtomContainer container, IAtom start, IAtom end) {
  
          List<IBond> startBonds = container.getConnectedBondsList(start);
          List<IBond> endBonds = container.getConnectedBondsList(end);
  
          if (startBonds.size() < 2 || endBonds.size() < 2) return null;
  
          if (has2DCoordinates(startBonds) && has2DCoordinates(endBonds)) {
              return axial2DEncoder(container, start, startBonds, end, endBonds);
          } else if (has3DCoordinates(startBonds) && has3DCoordinates(endBonds)) {
              return axial3DEncoder(container, start, startBonds, end, endBonds);
          }
  
          return null;
      }
docs: Create an encoder for axial 2D stereochemistry for the given start and
  end atoms.
  
  @param container the molecule
  @param start     start of the cumulated system
  @param end       end of the cumulated system
  @return an encoder or null if there are no coordinated