code: public final static void changePolymerNotation(int position, PolymerNotation polymer, HELM2Notation helm2notation) {
  		helm2notation.getListOfPolymers().set(position, polymer);
  	}
docs: method to change the PolymerNotation at a specific position of the
  HELM2Notation
  
  @param position
  position of the PolymerNotation
  @param polymer
  new PolymerNotation
  @param helm2notation
  input HELM2Notation