code: public final static List<PolymerNotation> getCHEMPolymers(List<PolymerNotation> polymers) {
      List<PolymerNotation> chemPolymers = new ArrayList<PolymerNotation>();
      for (PolymerNotation polymer : polymers) {
        if (polymer.getPolymerID() instanceof ChemEntity) {
          chemPolymers.add(polymer);
        }
      }
      return chemPolymers;
    }
docs: method to get all chem polymers given a list of PolymerNotation objects
  
  @param polymers List of PolymerNotation objects
  @return list of chem polymers