code: public final static void changeGroup(final GroupingNotation notation, final int position,
  			final HELM2Notation helm2notation) {
  		helm2notation.getListOfGroupings().set(position, notation);
  	}
docs: method to change a group of the HELM2Notation
  
  @param notation
  new group
  @param position
  position of the to be changed group
  @param helm2notation
  input HELM2Notation