code: List<IStereoElement> recognise(Set<Projection> projections) {
          
          if (!projections.contains(Projection.Fischer))
              return Collections.emptyList();
  
          // build atom index and only recognize 2D depictions
          Map<IAtom,Integer> atomToIndex = new HashMap<IAtom, Integer>();
          for (IAtom atom : container.atoms()) {
              if (atom.getPoint2d() == null)
                  return Collections.emptyList();
              atomToIndex.put(atom, atomToIndex.size());
          }
          
          RingSearch ringSearch = new RingSearch(container, graph);
          
          final List<IStereoElement> elements = new ArrayList<IStereoElement>(5);
  
          for (int v = 0; v < container.getAtomCount(); v++) {
  
              IAtom    focus = container.getAtom(v);
              Elements elem  = Elements.ofNumber(focus.getAtomicNumber());
  
              if (elem != Carbon)
                  continue;
              if (ringSearch.cyclic(v))
                  continue;
              if (stereocenters.elementType(v) != Tetracoordinate)
                  continue;
              if (!stereocenters.isStereocenter(v))
                  continue;
  
              ITetrahedralChirality element = newTetrahedralCenter(focus,
                                                                   neighbors(v, graph, bonds));
  
              if (element == null)
                  continue;
  
              // east/west bonds must be to terminal atoms
              IAtom east = element.getLigands()[EAST];
              IAtom west = element.getLigands()[WEST];
              
              if (!east.equals(focus) && !isTerminal(east, atomToIndex))
                  continue;
              if (!west.equals(focus) && !isTerminal(west, atomToIndex))
                  continue;
              
              elements.add(element);
          }
  
          return elements;
      }
docs: Recognise the tetrahedral stereochemistry in the provided structure.
  
  @param projections allowed projection types
  @return zero of more stereo elements